bluuebunny/crossref_metadata_2025 huggingface dataset:
Enzymatic cleavage of pro‐opiomelanocortin by anterior pituitary granules
Authors: Seidah N.G. , Pélaprat D. , Lazure C. , Chrétien M.
Published: July 2002

This paper presents the results obtained when pig anterior pituitary granule lysates are incubated with rat pro‐opiomelanocortin (POMC). The resultant peptides were analyzed by 3 systems of high‐performance liquid chromatography. This approach, when coupled with microsequence analysis of the conversion products, allowed the unambiguous identification of a major chymotryptic‐like activity (pH optimum around 8) associated with the granule lysates with a specificity directed towards selective Tyr‐X and Phe‐X bonds within the POMC molecule. Furthermore, these results also demonstrate that although the detected enzyme activity gives rise to products ‘resembling’ those expected, the characterization of the ‘elusive’ maturation enzyme responsible for the cleavage at pairs of basic residues remains to be critically evaluated.
Rat pancreatic ribonuclease: agreement between the corrected amino acid sequence and the sequence derived from its messenger RNA
Authors: Beintema Jaap J.
Published: July 2002

A corrected amino acid sequence of rat pancreatic ribonuclease is presented which is in agreement with the messenger RNA sequence in [J. Biol. Chem. (1982) 257, 14582–14585]. The corrections do not change the general position of rat ribonuclease in trees which can be constructed for ribonuclease sequences, although they do place the rat sequence somewhat closer to the mouse sequence. The evolutionary rate of ribonuclease in the rodent family of the Muridae (rat and mouse) now has been calculated to be 140 nucleotide substitutions per 108 years per 100 codons, and still is one of the highest rates yet observed. The occurrence of 4 additional amino acids at the C‐terminus in several mammalian ribonucleases is in agreement with the position of a second stop codon in the 3' non‐coding region of the rat messenger RNA sequence.
Thymidine kinase genes and the induction of anti‐rival responses by interferon
Authors: Mengheri Elena , Esteban Mariano , Lewis John A.
Published: July 2002

A mouse fibroblast cell‐line deficient in thymidine kinase (Ltk(−) aprt(−)) fails to show an anti‐rival response when treated with interferon. After introduction of a viral tk gene into these cells the resultant clones showed normal responses to interferon. However, one such tk‐containing clone (C6) spontaneously lost its ability to respond to interferon by inducing an antiviral state although it retained its ability to induce the enzyme oligo(2′–5′ A)‐synthetase. This sub‐clone(6A) still expressed thymidine kinase activity but restriction endonuclease analysis indicated an alteration in the sequences flanking the exogenous viral tk gene. Our results suggest that a modification in the exogenous viral DNA sequences led to a loss of interferon sensitivity.
Membrane dynamics in human leukemia and lymphoma cells
Authors: Billard C. , Phan Dinh Tuy F. , Rosenfeld C. , Tapiero H.
Published: July 2002

Membrane dynamics of human leukemia and lymphoma cell lines were analyzed by investigating the effect of pH on fluorescence polarization (P) of the lipophilic probe diphenylhexatriene (DPH). The degree of P varied as a function of pH, depending on the cell lines. These variations were not detected in phospholipid vesicles. In addition, they were prevented by treatments with glutaraldehyde, sodium azide or phenylmethylsulfanyl fluoride, a specific protease inhibitor. Therefore, these P value changes might be influenced by protein modification.
Characterisation of Ca2+ transport activity by white adipose tissue mitochondria
Authors: Epping Ronald J. , Taylor Wayne M. , Bygrave Fyfe L.
Published: July 2002

Ca2+ transport in mitochondria isolated from rat white adipocytes has been examined and many of the properties found to be similar to those reported for mitochondria isolated from rat liver. Ca2+ transport is ruthenium red‐sensitive (K
i ∼5 pmol.mg protein−1), the affinity for free Ca2+ is high (K
m ∼3.3 μM) and the V
max is 135 nmol Ca2+.min−1.mg protein−1 at 4°C with 0.2 mM Pi present. Ca2+ transport is stimulated by increasing the medium [Pi], and is inhibited when ATP or Mg2+ is added to the incubation system and in contrast to brown adipocyte mitochondria, Ca2+ efflux is not promoted by Na+. White adipocyte mitochondria may play a rôle in the regulation of total cell calcium in this tissue.
Monoclonal antibodies inhibiting RNA polymerase from Escherichia coli
Authors: Nikiforov V.G. , Yakubov L.Z. , Bogachova G.T. , Lebedev A.N. , Rokhlin O.V.
Published: July 2002

Monoclonal hybridoma antibodies directed against RNA polymerase from E. coli have been obtained. Only a few have been found to inhibit the enzyme activity. Antibodies produced by two clones, PYN‐1 and PYN‐2, inhibit RNA polymerase at the stage of RNA chain elongation. the PYN‐1 antibodies react with the β′‐subunit of the enzyme. The PYN‐2 antibodies react with the β‐subunit and with its 130 kDa amber fragment.
Subcellular localization of LH‐dependent phosphoproteins and their possible role in regulation of steroidogenesis in rat tumour Leydig cells
Authors: Bakker Ger H. , Hoogerbrugge Jos W. , Rommerts Focko F.G. , van der Molen Henk J.
Published: July 2002

Stimulation of rat tumour Leydig cells with LH resulted in phosphorylation of 7 proteins of 17, 22, 24, 33, 43, 57 and 76 kDa, and in dephosphorylation of a single protein of 20 kDa. The subcellular localization of these LH‐dependent phosphoproteins in combination with effects of inhibitors of microfilament formation and protein synthesis, suggest that phosphoproteins of 20, 43 and 76 kDa present in the cytosol may be involved in the action of microfilaments, whilst phosphoproteins of 24 and 33 kDa present in microsomes may be involved in specific protein synthesis.
Effect of acclimation temperature on the concentration of the mitochondrial ‘uncoupling’ protein measured by radioimmunoassay in mouse brown adipose tissue
Authors: Ashwell Margaret , Jennings Graham , Richard Denis , Stirling Dorothy M. , Trayhurn Paul
Published: July 2002

The effect of acclimation temperature on the concentration of the mitochondrial ‘uncoupling’ protein (M
r 32 000) from brown adipose tissue of mice has been investigated. The uncoupling protein was measured by a specific radioimmunoassay. Between 33°C (thermoneutrality) and −2°C there was a progressive increase with decreasing environmental temperature in the amount of uncoupling protein. For mice at −2°C the mitochondrial concentration of the protein was 9‐times higher than at 33°C, while the total amount of the protein in interscapulaar brown adipose tissue was estimated to be nearly 80‐times greater at −2°C compared to 33°C.
Oxidation of glutathione by free radical intermediates formed during peroxidase‐catalysed N‐demethylation reactions
Authors: Moldéus Peter , O'Brien Peter J. , Thor Hjördis , Berggren Margareta , Orrenius Sten
Published: July 2002

Horseradish peroxidase‐catalyzed N‐demethylation of aminopyrine and dimethylaniline results in generation of free radical intermediates which can interact with glutathione (GSH) to form a glutathione radical. This can either dimerize to yield glutathione disulfide or react with O2 to form oxygenated products of glutathione. Ethylmorphine is not a substrate in the peroxidase‐mediated reaction, and free radical intermediates which react with GSH, are not formed from aminopyrine and dimethylaniline when the horseradish peroxidase/H2O2 system is replaced by liver microsomes and NADPH. Therefore, it appears unlikely that formation of free radical intermediates can be responsible for the depletion of GSH observed during N‐demethylation of several drugs in isolated liver cells.
Sequence homology between potato spindle tuber viroid and U3B snRNA
Authors: Kiss Tamás , Pósfai János , Solymosy Ferenc
Published: July 2002

Sequence homology was found by computer analysis between potato spindle tuber viroid (PSTV) RNA and U3B snRNA of Novikoff hepatoma cells. This homology is colinear in arrangement, extends in length to 81% of the entire U3B snRNA molecule and is involved in the PSTV molecule unique sites which, if depicted in terms of the secondary structure of the circular PSTV molecule, reveal a conspicuous regularity in their location. A strong relation in primary structure between PSTV and U3B snRNA is demonstrated by statistical analysis.
Activation of yeast mannan synthetase by α factor pheromone
Authors: Ruiz Teresa , Villanueva Julio R. , Rodriguez Luís
Published: July 2002

The Saccharomyces cerevisiae mating pheromone α factor induces the activation of yeast mannan synthetase both in vivo and in vitro. In vivo the activating effect of the pheromone on the synthetase is specific for cells of the a mating type, while in vitro α factor is able to exert its action on the synthetase of either cell type (MAT a, MAT α and MAT a/MAT α).
Sequence similarity between Rhodospirillum rubrum ribulose bisphosphate carboxylase/oxygenase and the large subunit of the plant enzyme
Authors: Reeck Gerald R. , Teller David C.
Published: July 2002

Computerized methods were used to analyze published sequence information from Rhodospirillum rubrum ribulose‐1,5‐bisphosphate carboxylase/oxygenase (RUBPCase) and the sequence of the large subunit of spinach RUBPCase. The sequences of 7 peptides from the bacterial enzyme were compared to the entire sequence of the spinach large subunit to find optimal alignments and test statistical significance. Several of the R. rubrum RUBPCase peptides align unambiguously with the spinach sequence, and the alignment of the largest peptide is clearly significant in a statistical sense. The total of 91 positions aligned with R. rubrum peptides includes 30 identities. Our analysis strongly suggests that the entire sequence of the R. rubrum enzyme, when completed, will be found to exhibit statistically significant similarity to the large subunit of plant RUBPCase.
Sequence of a cDNA clone encoding part of the small subunit of the ribulose‐1,5‐bisphosphate carboxylase of Nicotiana sylvestris
Authors: Pinck Lothaire , Fleck Jacqueline , Pinck Monique , Hadidane Rafik , Hirth Léon
Published: July 2002

The nucleotide sequence of the cDNA clone pSTV34 is reported. It codes for the 68 COOH‐terminal amino acids of the protein coding for the small subunit of the ribulose bisphosphate carboxylase and has a 3′ non‐translated region 195 base pairs long. In the coding region this clone is 72% homologous with the corresponding cDNA clone from Pisum sativum.
Stimulation by epidermal growth factor of phospholipid methyltransferase in isolated rat hepatocytes
Authors: Chiva Vicente Alvarez , Cao Dolores Marin , Mato Jose M.
Published: July 2002

These results indicate a possible role of phospholipid methylation during liver proliferation.
Hormone‐responsive myofibrillar protease activity in cultured rat myoblasts
Authors: Mayer M. , Chaouat M. , Lernau O.Z. , Nissan S.
Published: July 2002

The effect of exposure to dexamethasone and serum‐deprivation on myofibrillar protease activity was determined by following cleavage of [14C]globin by isolated myofibrils obtained from rat skeletal muscle in culture. Dexamethasone [10−7M] produced a 46% increase in protease activity, and serum‐deprivation caused a 50% increase in activity over that of the enzyme in control cultures. The increases in proteolysis occurred concurrently with increased rate of overall protein degradation in these cells and were not associated with changes in cell viability. In cultured rat cardiac muscle cells dexamethasone failed to enhance myofibrillar protease activity, while serum‐deprivation produced a 52% increase in the enzyme activity. Addition of insulin (50 mU/ml) to the cultures did not affect proteolysis or myofibrillar protease activity, but completely prevented the dexamethasone‐induced increase of these activities. This effect of insulin suggests that the increase of muscle proteolysis in insulin‐deficient diabetic animals reflects an enhanced response of the muscle to circulating glucocorticoids rather than a direct effect of insulin‐deprivation on muscle proteolysis. Taken together, the present observations indicate that muscle cells in culture retain the ability to respond to catabolic stimuli by adaptive changes in the myofibrillar protease activity in a manner analogous to that of their parent tissue in the intact animal.
A topological model for chromatin transcription and a role for nucleosome linkers
Authors: Grigoryev Sergei A. , Krasheninnikov Igor A.
Published: July 2002

There is a good deal of evidence that transcribing RNA polymerase may translocate across nucleosomes without their displacement and (or) rearrangement. A topological model for RNA chain elongation on a nucleosome is considered here. A new mechanism of RNA polymerase translocation is suggested in order to avoid the steric hindrances inherent in the model. It is shown that a transcribed nucleoprotein fiber should be interrupted by protein‐free DNA stretches (nucleosome linkers) to allow release of nascent RNA. Possible verificiations and consequences of the model are discussed.
The presence of cytochrome c1 in the purple sulfur bacterium Chromatium vinosum
Authors: Gaul Dale F. , Knaff David B.
Published: July 2002

A cytochrome‐enriched preparation derived from Chromatium vinosum chromatophores has been used to demonstrate the presence of a previously undetected high potential cytochrome c in C. vinosum. The reduced cytochrome has α, β and Soret band maxima at 552–553, 523 and 422 nm respectively and a probable M
r of 31 000. The cytochrome appears to have E
m near +245 mV. These properties of the C. vinosum cytochrome suggest that it is similar to cytochrome c
1.
The role of 1‐O‐alkyl‐2‐acetyl‐sn‐glyceryl‐3‐phosphorylcholine (AcGEPC) and palmitoyl‐lysophosphatidate in the responses of human blood platelets to collagen and thrombin
Authors: Hallam T.J. , Scrutton M.C. , Wallis R.B.
Published: July 2002

Desensitisation of human blood platelets to the effects of 1‐O‐alkyl‐2‐acetyl‐sn‐glyceryl‐3‐phosphorylcholine (1‐O‐alkylAcGEPC) and palmityl‐lysophosphatidate by pre‐incubation with these agonists has no effect on the aggregatory or secretory responses to collagen but causes 30–40% inhibition of these responses to thrombin in aspirin‐treated platelets. The effects of 1‐O‐alkylAcGEPC and palmitoyl‐lysophosphatidate are not additive. The results are not consistent with the proposal that 1‐O‐alkylAcGEPC or lysophosphatidate are the mediators for the responses to collagen observed when prostaglandinendo‐peroxide synthesis is prevented, although they may play some role in the responses to thrombin under these conditions.
Interaction of rhodanese with intermediates of oxygen reduction
Authors: Cannella Carlo , Berni Rodolfo , D'Ottavio Palmerino
Published: July 2002

Cyanide‐promoted inactivation of the enzyme rhodanese [thiosulfate sulfurtransferase (EC 2.8.1.1)] in the presence of ketoaldehydes is caused by reduced forms of molecular oxygen generated during autoxidation of the reaction products. The requirement of both catalase and superoxide dismutase to prevent rhodanese inactivation indicates that hydroxyl radical could be the most efficient inactivating agent. Rhodanese, also in the less stable sulfur‐free form, shows a different sensitivity towards oxygen activated species. While the enzyme is unaffected by superoxide radical, it is rapidly inactivated by hydrogen peroxide. The extent of inactivation depends on the molar ratio between sulfur‐free enzyme and oxidizing agent. Fully inactive enzyme is reactivated by reduction with its substrate thiosulfate.
Characterization of oligosaccharides from the urine of loco‐intoxicated sheep
Authors: Sadeh Shoshana , Warren Christopher D. , Daniel Peter F. , Bugge Birgitte , James Lynn F. , Jeanloz Roger W.
Published: July 2002

Two major oligosaccharides were isolated by preparative HPLC from the urine of a locoweed‐fed sheep. Analysis by gas‐liquid chromatography and mass‐spectrometry indicated compositions of (Man)4(GlcNAc)2 and (Man)5(GlcNAc)2, respectively. Structures were determined by digestion with α‐D‐mannosidase and endo‐β‐N‐acetylglucosaminidases D and H, and comparison of the products by HPLC with synthetic standards, and oligosaccharides isolated from human mannosidosis urine. Incubation with an exo‐β‐N‐acetylglucosaminidase was without effect.
Decarboxylated bone Gla‐protein as a substrate for hepatic vitamin K‐dependent carboxylase
Authors: Vermeer Cees , Soute Berry A.M. , Hendrix Hans , de Boer-van den Berg Marian A.G.
Published: July 2002

Bovine bone Gla‐protein (B.G.P.) was prepared and decarboxylated into descarboxy‐B.G.P. (d‐B.G.P.). The latter was purified and identified as decarboxylated osteocalcin. Both crude and purified d‐B.G.P. are good substrates for vitamin K‐dependent carboxylase. Because the K
m of this enzyme for d‐B.G.P. is low, the latter is a better substrate than the frequently used pentapeptide F L E E L or exogenous protein substrates such as descarboxyprothrombin.
Ethylrhodamine as a fluorescent penetrating cation and a membrane potential‐sensitive probe in cyanobacterial cells
Authors: Severina Inna I. , Skulachev Vladimir P.
Published: July 2002

Ethylrhodamine, a homolog of rhodamine 123, was found to generate a diffusion potential across a planar bilayer phospholipid membrane (the compartment with the lower ethylrhodamine concentration positive). Addition of a penetrating synthetic anion increased the sensitivity of the membrane to ethylrhodamine, an effect similar to that previously described for triphenylmethylammonium, tetraphenylphosphonium and other synthetic penetrating cations. In experiments with the filamentous multicellular cyanobacteria Phormidium uncinatum, ethylrhodamine was used as a cationic penetrant and vital fluorescent probe for membrane potential (δΨ). It is shown that a treatment increasing protonic potential (illumination) and converting δpH to δΨ (nigericin) enhanced the fluorescence of cyanobacteria, as ethylrhodamine accumulated inside the cells. Uncouplers discharging δΨ completely abolished the fluorescence increase. Individual variations in the fluorescence of cells composing cyanobacterial trichomes could be observed. Illumination of a small part of a trichome with a narrow beam of the light actuating photosynthesis was shown to induce a fluorescence increase in both illuminated and non‐illuminated regions of this trichome, indicating δΨ transmission from cell to cell.
Protein‐free models for the proton‐coupled reduction of haemoproteins
Authors: Baldwin David A. , Campbell Vivien M. , Marques Helder M. , Pratt John M.
Published: July 2002

Reduction of the bis‐pilocarpate—haemin complex at pH ⩾ 10 involves the simultaneous uptake of an electron by the Fe(III) ion and a proton by the pendant alkoxide group of an axial ligand. This provides a protein‐free model for reactions such as the proton‐coupled reduction of cytochromes which involve cooperative Coulombic interaction between two non‐bonded sites.
Novel inhibition of carbonic anhydrase isozymes I, II and III by carbamoyl phosphate
Authors: Carter N.D. , Chegwidden W.R. , Hewett-Emmett D. , Jeffery S. , Shiels A. , Tashian R.E.
Published: July 2002

Carbamoyl phosphate has been shown to inhibit carbonic anhydrase (CA) isozymes CA I, CA II and CA III. This physiologically important molecule is the most potent, naturally occurring inhibitor of carbonic anhydrase yet found. It is also unique, among carbonic anhydrase inhibitors discovered hitherto, in that it inhibits the 3 isozymes with equal effect, despite their strikingly different properties. The results imply the participation of carbonic anhydrase in the regulation of substrate availability for the urea cycle.
S‐Adenosyl‐L‐homocysteine hydrolase from Dictyostelium discoideum is inactivated by cAMP and reactivated by NAD+
Authors: Hohman Robert J. , Veron Michel
Published: July 2002

Purified S‐adenosyl‐L‐homocysteine hydrolase from Dictyostelium discoideum is inactivated when incubated at 25°C with cAMP. Half maximal velocity of the inactivation process occurs at 10 μM cAMP. Catalytic activity is fully restored by further incubation with NAD+, but not with NADP+ or NADH. The enzyme must be preincubated with cAMP or NAD+ to induce inactivation or reactivation, respectively, since neither of these ligands has an effect on the active or inactive enzyme when added directly to the assay. These results suggest a role for cAMP and NAD+ in the regulation of cellular methylation reactions by altering the level of S‐adenosyl‐L‐homocysteine via S‐adenosyl‐L‐homocysteine hydrolase.
‘Molecular sandwiches’ as a basis for structural and functional similarities of interferons, MSH, ACTH, LHRH, myelin basic protein, and albumins
Authors: Root-Bernstein Robert Scott
Published: July 2002

Sequential similarities between the tryptohan peptide of myelin basic protein (residues 111–121), luteinizing hormone releasing hormone, melanotropin, adrenocorticotropin (residues 1–13), human leukocyte interferon (residues 28–40), and various segments of human and bovine serum albumin and hen ovalbumin are presented. It is suggested that these structural similarities may explain observations concerning common functional characteristics such as serotonin modulation, immunological activity with the adjuvant muramyl dipeptide, immunological cross‐reactivity, and the possible MSH‐ACTH‐like activity of a pepsin‐derived peptide of interferon.
Differences in polypeptide composition and enzyme activity between cold‐stable and cold‐labile microtubules and study of microtubule alkaline phosphatase activity
Authors: Hesketh J.E.
Published: July 2002

Cold‐stable and cold‐labile microtubules were prepared by two cycles of assembly and disassembly and two periods of exposure to cold. The cold‐labile preparations were shown to contain a higher proportion of a high molecular mass microtubule‐associated protein (MAP 2) than cold‐stable preparations. The cold‐stable preparations showed a much higher alkaline phosphatase activity. Stimulation of microtubule assembly by zinc led to increases in both cold stability and alkaline phosphatase activity.
Aspartic acid‐121 functions at the active site of bovine pancreatic ribonuclease
Authors: Stern Mary S. , Doscher Marilynn S.
Published: July 2002

The fully active semisynthetic enzyme formed by the non‐covalent interaction of residues 1–118 of bovine pancreatic ribonuclease and a synthetic tetradecapeptide containing residues 111–124 of the enzyme has allowed a direct test of the role of aspartic acid‐121 in the functioning of the molecule. Replacement of this residue by asparagine results in a derivative that is 4.5% active against cytidine 2',3'‐cyclic phosphate at pH 7.0 under standard assay conditions. Further studies with the same substrate at pH 5.8 reveal that the reduced activity results entirely from a diminished catalytic efficiency and not from a decreased affinity for substrate.
Activation of cGMP phosphodiesterase by purified green rod pigment from frog retina
Authors: Shinozawa Takao , Makino-Tasaka Momoyo , Suzuki Tatsuo
Published: July 2002

Activation of cGMP phosphodiesterase(PDE) of frog rod outer segments (ROS) by purified green rod pigment (GRP) was analyzed. GRP activated PDE in a similar manner to purified rhodopsin. This activation required illumination of the pigment and presence of GTP.
Hypophysectomy abolishes sexual dimorphism of liver carbonic anhydrase III
Authors: Jeffery S. , Carter N.D. , Wilson C.A.
Published: July 2002

Hypophysectomy was found to have no effect on the concentration of carbonic anhydrase III (CAIII) in male rat liver, whereas in the female, CAIII was elevated 10‐fold, to male levels.
A tissue‐specific transcription enhancer element in the human immunoglobulin λ light chain locus
Authors: Spandidos Demetrios A. , Anderson Margaret L.M.
Published: July 2002

An 8.0‐kb EcoRI fragment of the human immunoglobulin (Ig) λ light chain locus carrying the Ke−Oz− and Ke−Oz+ constant region genes and flanking sequences was studied for the presence of a transcriptional enhancer. Two types of assays were used. In the first, we measured the ability of recombinant plasmids carrying the 8.0‐kb Ig fragment covalently linked to the aminoglycoside phosphotransferase (aph) gene to transform mouse myeloma or mouse fibroblast cells to geneticin resistance. In the second, we used RNA spot and Northern blot hybridization analyses to determine the relative levels of aph specific RNA transiently expressed after DNA transfection. In fibroblast cells, the transformation frequencies were independent of the presence of the Ig fragment in the vector and there was no difference in the level of transient expression of the aph gene. In myeloma cells, the Ig fragment enhanced at least 10‐fold both the number of transformants and the level of aph gene expression over that obtained with vector alone. These results indicate the presence of a tissue‐specific transcriptional enhancer in the 8.0‐kb EcoRI fragment of the human Ig Cλ locus.
The H+/O ratio of proton translocation linked to the oxidation of succinate by mitochondria
Authors: Krab Klaas , Soos Jozsef , Wikström Mårten
Published: July 2002

In a recent communication Lehninger and co‐workers (Costa L.E., Reynaferje B., and Lehninger A.L. (1984) J. Biol. Chem. 259, 4802‐4811) reported values approaching 8 for the H+/O ratio of vectorial proton ejection from rat liver mitochondria respiring with succinate. Here we present a rigorous analysis of these measurements which reveals that they may significantly overestimate the true H+/O stoicheiometry.
PHI‐like immunoreactivity in the gallbladder and in vitro effect of porcine PHI on smooth muscle of the gallbladder
Authors: Yiangou Y. , Christofides N.D. , Gu J. , Piper P.J. , Polak J.M. , Bloom S.R.
Published: July 2002

The occurrence and distribution of PHI‐like immunoreactivity in the guinea pig gallbladder has been analysed by radioimmunoassay and immunocytochemistry. Chromatography of gallbladder extracts by gel permeation and high‐performance liquid chromatography revealed that guinea pig PHI‐like immunoreactivity is of a similar size to that of porcine PHI but may differ in its amino acid sequence. Immunocytochemistry showed PHI‐immunoreactivity to be localised to nerves found predominantly in the ganglionated plexus and themucosal plexus of the gallbladder. Pure natural porcine PHI induced a dose‐dependent relaxation of the isolated guinea pig gallbladder muscle which was not blocked by antagonists to acetylcholine, catecholamines, histamine, and 5‐hydroxytryptamine. PHI may thus be one of the local factors involved in controlling gallbladder function.
Physico‐chemical properties of the hydroxysterol binding protein of human lymphocyte cytosol
Authors: Defay R. , Astruc M. , Beseme F. , Descomps B. , de Paulet A.Crastes
Published: July 2002

Hydroxysterol
Human lymphocyte
Specific binding protein
Cell division
Insulin‐stimulated high affinity cyclic AMP phosphodiesterase in rat mammary acini
Authors: Aitchison Robert , West David W. , Clegg Roger A.
Published: July 2002

High affinity cyclic AMP phosphodiesterase activity in preparation of acini isolated from mammary tissue of lactating rats is shown to be stimulated by the addition of physiological concentrations of insulin to incubations of acini in vitro. This effect is expressed specifically on membrane‐associated phosphodiesterase and occurs in the absence of concurrent protein synthesis. The possible functional role of this aspect of insulin's action on mammary tissue is discussed and compared with the well‐known reversal by this hormone of the effects of lipolytic agents in adipose tissue and liver.
DNA rearrangements generating artificial promoters
Authors: Gragerov A.I. , Smirnov O.Yu. , Mekhedov S.L. , Nikiforov V.G. , Chuvpilo S.A. , Korobko V.G.
Published: July 2002

The promoter‐cloning plasmid pBRH4 (a derivative of pBR322 with a partially deleted promoter of the tet gene) is shown to contain a sequence which is located near the EcoRI site and can operate as an effective Pribnow box, but is not the remainder of the deletion‐inactivated tet promoter of pBR322. If there is a sequence homologous to the ‘−35’ promoter region at the border of the DNA fragment inserted at the EcoRI site, then a compound promoter arises and activates the tet gene. Point mutations in the nonfunctional −35 region of pBRH4 also activate the cryptic Pribnow box. Several compound promoters were obtained through deleting small portions of DNA around the HindIII site of pBR322; the deletions moved various sequences that could operate as Pribnow boxes towards the −35 region of the tet promoter.
Fluorescence changes from single striated muscle fibres injected with labelled troponin C (TnCDANZ)
Authors: Griffiths P.J. , Potter J.D. , Coles B. , Strang P. , Ashley C.C.
Published: July 2002

A fluorescently labelled derivative of the calcium binding subunit of troponin, TnC, has been injected into isolated striated muscle fibres from the barnacle Balanus nubilus. The Ca2+ affinity of isolated TnC is close to that of intact troponin when located in the thin filament. Excitation of the TnCDANZ within the muscle cell (325nm) revealed a marked fluorescence at 510 nm and was similar to that observed in vitro, which was absent at 400 or 600 nm after subtraction of the fibre autofluorescence. High Ca2+ salines increased the fluorescence at 510 nm by roughly 2 times. Single voltage clamp pulses produced a rapid rise in fluorescence at 510 nm after allowing for any non‐specific changes at 400 nm, and this signal preceded force development by approx. 55 ms at 22° C. It reached a maximum at the same time as force and subsequently decayed more slowly. The fluorescence signal increased in magnitude with increase in stimulus intensity. These results suggest that Ca2+ attaches rapidly to the contractile filament, but is lost relatively slowly and imply a slow decay of the activation process.
Interaction of α2‐macroglobulin‐bound thrombin with hirudin
Authors: Pochon François , Steinbuch Marion
Published: July 2002

The human thrombin bound to α2‐macroglobulin (α2 M) in a 1:1 stoichiometry is still able to interact with one of its specific inhibitors, hirudin. The dissociation constant of the complex hirudin‐α2M‐bound thrombin is 1 × 10−7 M, whatever the mode of thrombin binding, covalent or non‐covalent.
CTP can replace GTP in reactions catalyzed by eukaryotic peptide elongation factor 1
Authors: Tuháčková Z. , Havránek M. , Hradec J.
Published: July 2002

In several reactions catalyzed by highly purified peptide elongation factor 1 from rabbit reticulocytes, GTP may be fully replaced by CTP but not by ATP or UTP. This holds true for the factor‐dependent binding of aminoacyl‐tRNA to ribosomes, GTPase activity, GTP‐dependent autophosphorylation of the factor protein and binding of cholesteryl 14‐methylhexadecanoate by the factor.
The effect of EDTA on the apparent hysteretic properties of pyruvate carboxylase from Rhizopus arrhizus
Authors: Osmani Stephen A. , Scrutton Michael C.
Published: July 2002

Pyruvate carboxylase purified from Rhizopus arrhizus in the presence of 1 mM EDTA shows markedly nonlinear progress curves when assayed in the presence of acetyl‐CoA (activator) or L‐aspartate (inhibitor). The non‐linear progress curves are not abolished by preincubation of the enzyme with substrates, activator or inhibitor. Activation by acetyl‐CoA is prevented and can be reversed by the addition of EDTA. Enzyme purified in the absence of EDTA is immediately responsive to activation by acetyl‐CoA and inhibition by L‐aspartate and shows linear progress curves. Incubation of such an enzyme with EDTA induces properties characteristic of the preparation purified in the presence of this chelating agent. Tight binding of EDTA to the enzyme could not be demonstrated.
An Sau3AI restriction endonuclease isoschizomer from Bacillus cereus
Authors: Cruz A.K. , Kidane G. , Pires M.Q. , Rabinovitch L. , Guaycurus T.V. , Morel C.M.
Published: July 2002

The isolation and characterization of a restriction endonuclease from Bacillus cereus IOC 243 are described. The enzyme recognizes the palindromic sequence 5'‐G(met‐A,A)TC‐3' as determined by PEI chromatography of pancreatic DNase, snake venom phosphodiesterase digestion products of labelled fragments, analysis of restriction digests from normal and N6‐methyladenine‐free DNA and direct sequence analysis of cloned fragments. The staggered cleavage products with 5'‐terminal pGATC extensions are efficiently labelled with polynucleotide kinase and are easily cloned into BamHI sites. The enzyme, denoted Bce243, is thus an isoschizomer of Sau3AI. Its use and potential advantages in substituting Sau3AI are discussed.
Expression of cloned cDNA for a major surface antigen of Plasmodium falciparum merozoites
Authors: Odink Karel G. , Lockyer Michael J. , Nicholls Stephen C. , Hillman Yvonne , Freeman Robert R. , Holder Anthony A.
Published: July 2002

A cDNA library of P. falciparum was constructed. Using size‐selected mRNA as a probe several clones were isolated which hybridized to mRNAs larger than 5 kilobases (kb). The cDNA insert of pFC 17, which hybridizes to 5.6‐kb mRNA was expressed by fusion to anthranilate synthetase I in a plasmid expression vector. The expressed fusion protein was shown to contain epitopes of a 195‐kDa protein which is the precursor to 3 major surface antigens of P. falciparum merozoites.
Cleavage of oligosaccharides by rat kidney sialidase Influence of substrate structure
Authors: Cohen-Forterre L. , Mozère G. , André J. , Sternberg M.
Published: July 2002

The specificity of the sialidase activity present in rat kidney cortex (12 000 × g pellet) was studied with various tritiated oligosaccharidic substrates: (i) αNeuAc2 → 3βGall → 4Glc‐itol[3H], αNeuAc2 → 6βGall → 4Glc‐itol[3H] and αNeuAc2 → 8αNeuAc2 → 3βGall → 4Glc‐itol[3H] from bovine colostrum; (ii) α‐NeuAc2 → 6βGall → 4βGlcNAc‐itol[3H], αNeuAc2 → 3βGal1 → 4βGlcNAcl → 2αManl → 3βMan1 → 4GlcNAc‐itol[3H]. αNeuAc2 → 6βGall → 4βGlcNAcl → 2αManl α 3(βGall → 4GlcNAcl → 2αManl → 6)βManl → 4GlcNAc‐itol [3H]et αNeuAc2 → 6βGall → 4βGlcNAcl → 2αManl‐3(αNeuAc2 → 6βGall → 4βGlcNAcl → 2αManl → 6)βManl 4GlNAc‐itol[3H] isolated from the urine of a patient with mucolipidosis I. The enzyme cleaves α2 → 3 and α2 → 8 linkages at a greater rate than the α2 → 6 bonds. Its activity decreases with the length of the oligosaccharidic chain. Substitution of a glucose moiety by Nacetylglucosamine results in diminished activity. The specificity of rat kidney sialidase differs from that reported for other mammalian of viral sialidases.
L‐α‐Amino‐β‐thio‐ϵ‐caprolactam, a new sulfur‐containing Substrate for α‐amino‐ϵ‐caprolactam racemase
Authors: Ahmed Syed Ashrafuddin , Esaki Nobuyoshi , Tanaka Hidehiko , Soda Kenji
Published: July 2002

A one‐step synthesis of a new sulfur‐containing compound, L‐α‐amino‐β‐thio‐ϵ‐caprolactam from L‐cysteine methyl ester and 2‐chloroethylamine has been described. This intramolecular cyclic amide of S‐(β‐aminoethyl)‐L‐cysteine serves as a good substrate for α‐amino‐ϵ‐caprolactam racemase. L‐α‐Amino‐β‐thio‐ϵ‐caprolactam is racemized more than 3 times faster and binds about 4‐fold stronger to the enzyme than L‐α‐amino‐ϵ‐caprolactam itself. Optimum pH for racemization of this new compound is about 10.0.
Interaction of the HMG1 protein with nucleic acids
Authors: Shepelev V.A. , Kosaganov Yu.N. , Lazurkin Yu.S.
Published: July 2002

Binding constants have been measured for the interaction of the protein HMG1 with native DNA, denatured DNA and a number of polynucleotides at near‐physiological ionic strengths, using gel filtration and thermal denaturation. The interaction of HMG1 with DNA is shown to be noncooperative and reversible. Nucleic acids form the following series in order of increasing binding constants: poly(U) ∞ poly(A) < poly(dA) < dsDNA ∞ poly(dA) · poly(dT) ∞ poly(dG) · poly(dC) « poly[d(A‐T)] ∞ ssDNA.
The synthesis of ribosomal RNA and ribosomal protein and their incorporation into ribosomes in the uterus of the oestrogen‐stimulated immature rat
Authors: Muller R.E. , Knowler John T.
Published: July 2002

Cell‐free protein sysnthesis
Immunoassay
Complete separation and quantitative determination of DABTH‐amino acid derivatives by isocratic reversed‐phase high performance liquid chromatography
Authors: Lehmann Arnold , Wittmann-Liebold Brigitte
Published: July 2002

The isocratic separation by reversed‐phase HPLC of all DABTH‐amino acid derivatives which are released by degradation of polypeptides with 4‐N,N‐dimethylaminobenzene‐4'‐isothiocyanate is described. The method allows an easy and quick identification and the quantitative determination of all derivatives in 30 min and includes the separation of isoleucine and leucine. Detection limit is 5 pmol at 436 nm. The solvent mixture is continuously recycled through the column, thereby reducing the solvent consumption considerably.
The effect of phallotoxins on the structure of F‐actin in myosin‐free ghost muscle fibres of rabbit
Authors: Borovikov Yu.S. , Bukatina A.E. , Son'kir B.Ja.
Published: July 2002

Using polarized UV fluorescent microscopy it has been shown that phallotoxins (phalloidin‐sulfone, phalloidin‐sulfoxide‐B, phalloidin‐sulfoxide‐A and dithio‐phalloidin) cause an increase in tryptophan fluorescence anisotropy of F‐actin myofilaments in myosin‐free ghost muscle fibres of rabbit. The results obtained are considered to be evidence of conformational changes in F‐actin, induced by phallotoxins. These changes are irreversible to a significant extent, which points to a high degree of actin binding to both toxic and nontoxic phallotoxins.
Studies in bile salt solutions
Authors: O'Connor Charmian J. , Wallace Robert G.
Published: July 2002

Stimulation of human milk lipase by deoxycholate and its taurine and glycine conjugates was demonstrated by measuring the esterolysis reaction of 4‐nitrophenylacetate. The steroidal surfactants did not bind strongly to the polar substrate but they did bind effectively to a hydrophobic site on the enzyme and these bile salt‐enzyme complexes were effective catalysts. These results are compared with those for stimulation of the enzyme by cholate surfactants and it has been demonstrated that the absence of a 7α‐OH substituent on the steriod nucleus does not prevent stimulation of either the esterolytic or lipolytic activity of the enzyme.
An opsonised electrode
Authors: Green Monika J. , Hill H.Allen O. , Tew David G. , Walton Nicholas J.
Published: July 2002

A pyrolytic graphite electrode was surface modified with human IgG and used as a stimulus to elicit a respiratory burst from human neutrophils. The oxidation current observed was shown to be due to re‐oxidation of superoxide produced by the neutrophils. Both superoxide dismutase and N‐ethylmaleimide were effective inhibitors of the oxidation current.
In vivo proton NMR spectroscopy
Authors: Doddrell David M. , Kathryn M Nicholls , Sanders Jeremy K.M.
Published: July 2002

The metabolism of [13C]formaldehyde in E.coli has been observed by proton NMR; the reverse‐POMMIE pulse sequence, which saturates all 1H signals and then transfer magnetisation from 13C to 1H, suppresses water by 105‐fold, allowing observation of metabolism at the millimolar level
Constraints of T conformation of carp azide hemoglobin on Fe site structure
Authors: Bianconi A. , Congiu-Castellano A. , Dell'Ariccia M. , Giovannelli A. , Morante S.
Published: July 2002

The iron site structure modifications induced by the transition from the quaternary R to T structure in ferric carp azide hemoglobin have been detected from analysis of multiple scattering resonances in the XANES (X‐ray absorption near edge structure) spectra. High signal‐to‐noise XANES spectra measured at the Frascati ‘wiggler’ synchrotron radiation facility reveal that the forces on the Fe active site, due to the transition from the R to T quaternary conformation, only induce the tilting of the porphyrin plane and probably also of the proximal histidine. The variation of the Fe‐N mean distance is not detected by XANES spectroscopy and therefore it is less than 0.01 Å.
A new hemoglobin variant, Hb Mito [β144(HC 1)Lys → Glu], with increased oxygen affinity
Authors: Harano Keiko , Harano Teruo , Ueda Satoshi , Ohkushi Toshihiro , Imai Kiyohiro
Published: July 2002

A new abnormal hemoglobin, Hb Mito [β144(HC 1)Lys → Glu], with an amino acid substitution in the 2,3‐DPG pocket, was discovered in a Japanese female. This hemoglobin showed increased oxygen affinity, and decreased organic phosphate and Bohr effects, while the Hill constant n was normal.
Aqueous micellar systems in membrane protein crystallization
Authors: Weckström Kristian
Published: July 2002

The effects of NaCl and polyethylene glycol (PEG) 4000 on the lower consolution boundary (LCB) of a nonionic surfactant (C8E5) were studied and compared. Micellar systems where NaCI and PEG 4000 are present are often used in membrane protein crystallization. While sodium chloride shifts the surfactant LCB to lower temperatures without a significant change in the shape of the boundary, PEG produces a large solubility change strongly depending on the surfactant concentration. The salt effect is explained by a reduced interaction of the micellar oligooxyethylene chains with the water and the PEG effect by an unfavourable configurational interaction between the C8E5 micelles and PEG molecules.
Fluorescent labelling of histone H3: effect on histone‐histone interaction and core particle assembly
Authors: Lindsey George G. , Thompson Patricia , Pretorius Linda , von Holt Claus
Published: July 2002

Substitution of Cys 110 of chicken histone H3 with N‐iodoacetyl‐N
1‐(5‐sulpho‐1‐naphthyl)ethylenediamine or iodoacetamide prevents octamer formation in 2 M NaCl but does not prevent polyglutamic acid‐mediated core particle assembly.
Effects of 1,25‐dihydroxycholecalciferol administration on the rat renal vitamin K‐dependent carboxylating system
Authors: Karl Peter I. , Carnes David L. , Friedman Paul A.
Published: July 2002

We have shown previously that the in vitro activity of the renal vitamin K‐dependent γ‐glutamyi carboxylase toward synthetic oligopeptide substrates is stimulated by administration of either parathyroid hormone (PTH) or 1,25‐dihydroxycholecalciferol [1,25 (OH)2D3] to rats [(1983) J. Biol. Chem. 258, 12783‐12786]. Here we report that administration of 1,25(OH)2D3 to rats increases their levels of endogenous carboxylase substrate as well. Rats fed a vitamin D‐deficient diet had highly elevated serum PTH levels while vitamin D‐replete animals had undetectable levels. Furthermore, since PTH increases 1,25(OH)2D3 levels by stimulating renal 25‐hydroxy vitamin D‐1α‐hydroxylase, it is very likely that the stimulatory effects of PTH on the renal vitamin K‐dependent carboxylating system are mediated by 1,25(OH);,D3.
Spin label studies of the essential sulfhydryl group environment in chicken liver fructose‐1,6‐bisphosphatase
Authors: Zeidan Henry , Han Peter , Johnson Joe
Published: July 2002

The local environment of the essential sulfhydryl groups in chicken liver fructose‐1,6‐bisphosphatase has been investigated by ESR techniques using a series of iodoacetamide spin labels, varying in chain length between the iodoacetate and nitroxide free radical group. The ESR spectrum of spin‐labeled chicken liver fructose‐1,6‐bisphosphatase showed that the sites of labeling were highly immobilized when the enzyme was chemically modified by spin label iodoacetate, suggesting that the sulfhydryl groups of the protein are in a small, confined environment. From the change in the ESR spectra of these nitroxides as a function of chain length, we conclude that the sulfhydryl group is located in a cleft approx. 10.5 Å in depth.
An unusual linkage between polysaccharides and some major proteins from the outer membrane of Escherichia coli
Authors: Barbas J.A. , Vázquez D. , Rodríguez-Tébar A.
Published: July 2002

(E. coli) Outer membrane
OmpA
Lipopolysaccharide
Site‐specific restriction endonuclease from the filamentous cyanobacterium Nostoc sp. MAC PCC 8009
Authors: Lau Reginald H. , Visentin Louis P. , Martin Stan M. , Hofman Jason D. , Doolittle W.Ford
Published: July 2002

We report here the presence of a type‐II restriction endonuclease in the filamentous cyanobacterium Nostoc sp. MAC PCC 8009. This restriction enzyme, NSp MAC I, is the first reported isoschizomer of BglII and is very readily purified from non‐specific deoxyribonuclease activity in the crude lysate by one round of phosphocellulose column chromatography.
Ganglioside headgroups decrease lipid order in reconstituted phosphatidylcholine liposomes
Authors: Ollmann Marika , Galla Hans-Joachim
Published: July 2002

The effect of oligosaccharide carrying lipids on membrane fluidity has been investigated. Gangliosides GM1 and GQ1 were reconstituted into phosphatidylcholine bilayer membranes at low concentrations ( < 5 mol%). A strong fluidizing effect was observed leading to a suppression of the phase transition temperature. This was most pronounced with highly sialylated gangliosides. Ca2+ reverses the effect due to phase separation phenomena. We assume a hydrophilic lipid‐lipid interaction in accordance with previously studied glycoprotein‐lipid interactions.
Search for a regulatory function of mitochondrial proteinases in yeast
Authors: Viard I. , Stahl A.J.C.
Published: July 2002

Proteolytic activity in yeast mitochondrial membranes and soluble fractions was studied using a labeled substrate: [14C]dimethylcasein. Optimal activity for the two fractions was at pH 6 in phosphate buffer at 37°C. Activity was partially inhibited by adding 3 mmol/1 ATP. Activity was enhanced rapidly in both fractions when yeast cells were grown aerobically on a derepression medium and transfered on a repression medium in anaerobiosis. Mitochondrial proteinase mediation in the mitochondrial breackdown observed during transition from aerobical derepression to anaerobical repression is discussed.
Sequence studies of peanut agglutinin
Authors: Lauwereys M. , Foriers A. , Sharor N. , Strosberg A.D.
Published: July 2002

Sequence studies have been performed on affinity purified peanut agglutinin, a galactose binding lectin. 161 residues have been compared to homologous residues in soybean agglutinin and favin. Extensive similarities have been uncovered, confirming the conservation of lectin sequences among all legume lectins. Evidence is presented for the existence of internal duplications and/or isolectins.
Insulin processing and action in adipocytes: evidence for generation of insulin‐containing vesicles by leupeptin and monensin
Authors: Jeffrey Ian W. , Flint David J. , Vernon Richard G. , Mayer R.John
Published: July 2002

Incubation of adipocytes with 125I‐insulin plus leupeptin or monensin, but not chloroquine, resulted in the appearance of a novel peak of 125I‐insulin (modal density about 1.20 ) on density gradient centrifugation; the appearance of the peak depended on the presence of specific insulin receptors on the cell surface. The fractions comprising this peak contained vesicles, probably originating from the Golgi apparatus, and dit not appear to be contaminated with lysosomes, mitochondria or plasma membrane. Entrapment of insulin in these vesicles per se did not prevent the activation of glucose transport, acetyl‐CoA carboxylase or pyruvate dehydrogenase by insulin.
Dephosphorylation of the deinhibitor protein by the PCSH protein phosphatase
Authors: Goris Jozef , Waelkens Etienne , Merlevede Wilfried
Published: July 2002

The deinhibitor protein, responsible for the decreased sensitivity of the ATP, Mg‐dependent protein phosphatase to inhibitor‐1 and the modulator protein, is inactivated by cyclic AMP‐dependent protein kinase and reactivated by dephosphorylation. The specificity of this reaction was tested with the ATP, Mg‐dependent phosphatase in its activated or spontaneously active form, four different forms of polycation‐stimulated phosphatases (PCSH, PCSM, PCSL and PCSC) and calcineurin. Only the high ‐M
r, polycation‐stimulated protein phosphatase (PCSH), but not its catalytic subunit (PCSC), shows a high degree of specificity for the deinhibitor protein. Deinhibitor phosphatase activity of PCSH is affected neither by polycations nor by Mn ions.