bluuebunny/crossref_metadata_2025 huggingface dataset:
Excretion of ecdysteroids by schistosomes as a marker of parasite infection
Authors: Nirde P. , De Reggi M.L. , Tsoupras G. , Torpier G. , Fressancourt P. , Capron A.
Published: July 2002

Ecdysteroids produced by schistosomes are released in biological fluids of infected hosts. In the sera, the concentration of ecdysteroids correlates with the perimissiveness of the host to schistosome infection and its detection is available in the absence of positive parasitological tests. In the urine, ecdysteroid concentration decreases markedly after chemotherapy. 20‐Hydroxyecdysone and its epimer were identified in the urine of infected patients using mass spectrometry. These data demonstrate for the first time that ecdysteroids are released by organisms. Moreover, they are potent molecules of parasite infection and can be used for parasite diagnosis.
The interaction of Bacillus protoplasts with sonicated phosphatidylcholine liposomes
Authors: Urbaneja M.A. , Villena A. , Goñi F.M.
Published: July 2002

When protoplasts from Bacillus subtilis are incubated with sonicated liposomes made from egg‐yolk phosphatidylcholine, this phospholipid is incorporated into the protoplast membranes. Biochemical, fluorescence and ultrastructural data suggest that incorporation occurs through membrane fusion.
Coordinated synthesis of the nuclear protein cyclin and DNA in serum‐stimulated quiescent 3T3 cells
Authors: Bravo R.
Published: July 2002

Quantitative two‐dimensional gel electrophoretic analysis (IEF) of the nuclear polypeptide cyclin together with autoradiographic studies have revealed a coordinate synthesis of cyclin and DNA after serum stimulation of quiescent 3T3 cells. These results strengthen the notion that cyclin may be a central component of the pathway(s) that regulate cell proliferation.
Virus genome integration as a function of the host cell genome replicative cycle
Authors: Eremenko Tamilla , Volpe Pietro
Published: July 2002

Mouse 3T3 cells were grown and synchronized in monolayer with the double thymidine block. Their infection with SV40 took place continuously during the cellular cycle. However, integration of viral DNA into host cell DNA occurred preferentially during the S phase. Phase G1 appeared to be necessary for virus‐cell DNA recombination in S phase. Phase G2 did not alter the stability of the integrated viral genome.
Tumor‐specific inhibition of DNA synthesis and cell proliferation by a factor from bovine placenta — possible mechanism
Authors: Letnansky Karl
Published: July 2002

A polypeptide isolated from the maternal part of bovine placentas inhibits significantly the incorporation of thymidine into the DNA of tumor cells. When normal cells are used, this effect is found only to a very limited degree. Surface membrane components have been identified which are enriched on tumor cells and which are responsible for a better binding of the inhibitor to tumor cells than to normal cells. After internalization of the receptor—inhibitor complex, a decrease in the nuclear content of two proteins is observed, which might be a requirement for the inhibition of the DNA synthesis.
Base‐specific ribonucleases potentially involved in heterogeneous nuclear RNA processing and poly(A) metabolism
Authors: Bachmann Michael , Schröder Heinz C. , Messer Rudolf , Müller Werner E.G.
Published: July 2002

Polyadenylation and splicing of heterogeneous nuclear RNA, two crucial steps in mRNA processing, are apparently enzymically mediated processes. This contribution summarizes the properties and the presumed functions of the known poly(A) catabolic enzymes (endoribonuclease IV and V, 2′,3′‐exoribonuclease) as well as those of the pyrimidine‐specific endoribonucleases associated with snRNP—hnRNP complexes (endoribonuclease VII, acidic pI 4.1 endoribonuclease and poly(U)‐specific U1 snRNP‐nuclease).
Cytochrome b reduction by hexaammineruthenium in mitochondria and submitochondrial particles
Authors: Kunz Wolfram S. , Konstantinov Alexander
Published: July 2002

In the presence of ascorbate, hexaamineruthenium mediates rapid reduction of cytochrome b‐562 in submitochondrial particles but not in mitochondria. The reaction is obsreved in the combined presence of antimycin (or funiculosin) and myxothiazol, which implies direct interaction of Ru(NH3)2+
6 with b cytochrome(s). We assume that contrary to previous conclusions (Case and Leigh (1976) Biochem. J., 160, 769‐783) redox centre of at least one of the oxidized cytochromes b, most probably of b‐562, is exposed to the M‐aqueous phase.
Precursor‐product relationship between the 26‐kDa and 18‐kDa fragments formed by iodination of human thyroglobulin
Authors: Marriq Claudine , Lejeune Pierre-Jean , Malthiery Yves , Rolland Marcel , Lissitzky Serge
Published: July 2002

At moderate iodination levels (20 iodine at atoms/molecule), human thyroglobulin (hTgb) produces after reduction a thyroxinyl‐peptide of 26 kDa which represents the N‐terminal part of the protein. At higher iodination levels, the 26‐kDa peptide is accompanied by another T4‐containing peptide of 18 kDa. A precursor‐product relationship between the 26‐ and 18‐kDa fragments was demonstrated by the study of the tryptic fragments of both hormonopeptides. In addition, comparison with the protein sequence deduced from the nucleotide sequence of the 5'‐end of hTgb mRNA demonstrated that the N‐terminal region of Htgb from which are issued the 26‐kDa peptide and its 18‐kDa derivative is especially sensitive to proteolysis. This character is possibly related with a facilitated release of thyroid hormones in vivo.
Evidence that the mitochondrial activator of phosphorylated branched‐chain 2‐oxoacid dehydrogenase complex is the dissociated E1 component of the complex
Authors: Yeaman Stephen J. , Cook Kenneth G. , Boyd Richard W. , Lawson Rowena
Published: July 2002

Branched‐chain 2‐oxoacid dehydrogenase complex is inactivated by phosphorylation of the α‐subunit of the E1 component of the complex. High‐speed supernatant from rat liver mitochondria contains an activator protein which can restore activity to the phosphorylated complex without concomitant dephosphorylation [(1982) FEBS Lett. 147, 35–39]. We report here several lines of evidence which indicate that activator is the dissociated non‐phosphorylated form of the E1 component.
Calmodulin binding to human spectrin
Authors: Berglund Åsa , Backman Lars , Shanbhag Vithaldas P.
Published: July 2002

Calmodulin is shown to interact with human spectrin dimer. The binding was highly calcium‐dependent and observed in two different kinds of experiments. Firstly, affinity chromatography of calmodulin on a Sepharose 4B column with immobilized spectrin, and secondly, partition in aqueous two‐phase polymer systems. In the column experiments stoichiometric amounts of calmodulin were retained on the spectrin‐Sepharose column when micromolar concentrations of calcium were present. The calmodulin bound could be eluted with EGTA. The partition coefficient of calmodulin in an aqueous two‐phase polymer system containing calcium was changed upon addition of spectrin, indicating an association between the two proteins. In the absence of calcium, spectrin did not cause any change in the partition behaviour of calmodulin, thus showing that the association requires calcium.
LHRH inactivation by reconstituted horse and fetal bovine sera: assessment by reduction of immunoreactivity and biological activity in pituitary cell cultures
Authors: O'Conner James L. , Lapp Carol A. , Clary Anthony R.
Published: July 2002

Lyophilized horse and fetal bovine sera are commonly incorporated into the growth media used for primary pituitary cell cultures. LHRH degrading activity has been assumed to exist in these preparations but has not actually been demonstrated. During our studies with pituitary cultures, it became necessary to ascertain if LHRH inactivating activity could be demonstrated in these sera. Luteinizing hormone releasing hormone (LHRH) was preincubated in either serum‐free medium or medium containing fetal bovine and horse serum. Whether LHRH was lost during these incubations was assessed by diminished immunoreactivity as indicated by radioimmunoassay (RIA) and by diminished biological activity as indicated by reduced release of LH from pituitary cell cultures. Both the RIA and bioassay results indicated LHRH inactivating activity; the loss of LHRH could be prevented by inclusion of bacitracin in the incubations.
Lack of a direct role for cyclic AMP in parathyrin action on phosphate reabsorption by the kidney
Authors: Parveen Riffat , Grahn Michael F. , Butterworth Peter J.
Published: July 2002

Isolated chick kidney proximal tubule cells have been used in a study of the mechanism by which PTH inhibits Na+‐dependent Pi transport in the kidney. Treatment with PTH inhibits Pi uptake by the cells by 13% and stimulates cyclic AMP production by 77%. Forskolin, a potent activator of adenyl cyclase, brought about an 11‐fold stimulation of cyclic AMP production by the cells, but in contrast to PTH, the drug had no effect on Na+‐dependent Pi uptake. These results provide evidence that PTH action on phosphate transport is not mediated by cyclic AMP.
Proton magnetic resonance studies of 7Fe ferredoxins
Authors: Nagayama K. , Ohmori D.
Published: July 2002

The oxidizability of a redox couple, [4Fe‐4S], in a 7Fe ferredoxin extracted from Pseudomonas ovalis was monitored by 1H‐NMR. The iron‐sulfur cluster in the ferredoxin was not only reducible (Nagayama et al., 1983) but also oxidizable in its native form. This result provided the first verification of 3 redox states for a redox center in ferredoxin, 4Fe, in the native form of the protein.
Tetraglycylferrichrome ‐ the first heptapeptide ferrichrome
Authors: Deml G. , Voges K. , Jung G. , Winkelmann G.
Published: July 2002

From a strain of Neovossia indien (Mitra) Mundk., a smut fungus of the order Tilletiales, a novel ferrichrome‐type siderophore was isolated. We have demonstrated that this is a heptapeptide rather than the usual hexapeptide, which contained, in addition to L‐ornithine, a (Gly)4 sequence instead of the (Gly)3 sequence usually found. Transport studies with 55Fe‐labelled (Gly)4‐ferrichrome and (Gly)3‐ferrichrome in Neurospora crassa revealed identical uptake rates, indicating that increased ring size and conformational flexibility of the peptide backbone are of minor importance during function and recognition by the ferrichrome transport system.
Thymidylate synthetase‐positive and ‐negative murine mammary FM3A carcinoma cells as a useful system for detecting thymidylate synthetase inhibitors
Authors: Balzarini J. , de Clercq E. , Ayusawa D. , Seno T.
Published: July 2002

The murine mammary FM3A/O and the thymidylate (dTMP) synthetase‐deficient FM3A/TS− carcinoma cell lines can be considered as a novel and useful test system for the detection of nucleoside analogues which are directly aimed at the thymidylate synthetase. These compounds should be inhibitory for FM3A/O but not for FM3A/TS− cells, and their inhibitory effects on FM3A/O cell growth should be readily reversed by exogenous dThd within the concentration range of 5–20 μM.
A hypothesis for the possible involvement of microtubules and protein kinase in the mechanism of action of cdc 28 gene product of Saccharomyces cerevisiae
Authors: Dudani Anil Kumar , Prasad Rajendra
Published: July 2002

Microtubule
Protein kinase
Growth control
G1 arrest
Cell cycle
Saccharomyces cerevisiae
EPR detected triplet formation in a single crystal of reaction center protein from the photosynthetic bacterium Rhodopseudomonas sphaeroides R‐26
Authors: Gast P. , Norris J.R.
Published: July 2002

Bacterial photosynthesis Rhodopseudomonas sphaeroides R‐26
EPR
Reaction center triplet
Protein crystal
Solubization of angiotensin II receptors in rat glomeruli
Authors: Chansel Dominique , Ardaillou Nicole , Ardaillou Raymond
Published: July 2002

125I‐labelled angiotensin II (A II) specifically binds to solubilized receptors extracted from rat isolated glomeruli using CHAPS (3‐[3‐(cholamidopropyl)dimethylammonio]‐1‐propanesulfonate). The yield of solubilization of the binding sites was 3.3%. Equilibrium was reached after 15–20 min and specific binding represented 75% of total binding. Dissociation of the hormone—receptor complex after addition of an excess of A II was very slow in the presence of Ca2+ and Mg2+. [Sar1 Ala8] A II and [Sar1 Ile8] A II were more potent as competitive inhibitors of 125I‐labelled A II than A II itself and its heptapeptide. These basic features of 125I‐labelled A II binding to the extracted material were similar to those observed previously with untreated glomeruli.
Water‐soluble 17 and 23 kDa polypeptides restore oxygen evolution activity by creating a high‐affinity binding site for Ca2+ on the oxidizing side of Photosystem II
Authors: Ghanotakis Demetrios F. , Topper James N. , Babcock Gerald T. , Yocum Charles F.
Published: July 2002

Exposure of detergent‐isolated preparations of the Photosystem II complex to 2 M NaCl releases water‐soluble 17 and 23 kDa polypeptides; the inhibited rate of oxygen evolution activity is stimulated by addition of Ca2+ [(1984) FEBS Lett. 167, 127–130]. Reactivation of oxygen evolution activity by Ca2+ requires the presence of the ion in high (mM) non‐physiological concentrations. Using a new dialysis‐reconstitution procedure we have shown that rebinding of the 17 and 23 kDa polypeptides restores oxygen evolution activity only when the system has not been pretreated with EGTA. Removal of loosely‐bound Ca2+ from the salt‐extracted PS II complex and from the polypeptide solution, by dialysis against EGTA, blocks reconstitution of oxygen evolution activity even though the two polypeptides do rebind; restoration of Ca2+ to EGTA‐treated systems, after rebinding of the 17 and 23 kDa polypeptides, results in a strong reconstitution of oxygen evolution activity. The effect of rebound 17 and 23 kDa polypeptides is to promote high affinity binding of Ca2+ to the reconstituted membrane.
The H+/O ratio of proton translocation linked to the oxidation of succinate by mitochondria
Authors: Lehninger Albert L. , Reynafarje Baltazar , Hendler Richard W. , Shrager Richard I.
Published: July 2002

Costa, L.E., Reynafarje, B. and Lehninger, A.L. [(1984) J. Biol. Chem. 259, 4802‐4811] have reported ‘second‐generation’ measurements of the H+/O ratio approaching 8.0 for vectorial H+ translocation coupled to succinate oxidation by rat liver mitochondria. In a Commentary in this Journal [Krab, K., Soos, J. and Wikström, M. (1984) FEBS Lett. 178, 187‐192] it was concluded that the measurements of Costa et al. significantly overestimated the true H+/O stoichiometry. It is shown here that the mathematical simulation on which Krab et al. based this claim is faulty and that data reported by Costa et al. had already excluded the criticism advanced by Krab et al. Also reported are new data, obtained under conditions in which the arguments of Krab et al. are irrelevant, which confirm that the H+/O ratio for succinate oxidation extrapolated to level flow is close to 8.
Pyruvate carboxylase from Rhizopus arrhizus
Authors: Mayer F. , Osmani S.A. , Scrutton M.C.
Published: July 2002

Pyruvate carboxylase purified from Rhizopus arrhizus exhibits projections when examined in the electron microscope which indicate that this enzyme is a tetrameric molecule in which the subunits are arranged at the corners of a tetrahedron. The tetrameric molecule is stabilised by addition of acetyl‐CoA or of pyruvate but is labilised in the presence of 2‐oxoadipate. Addition of EDTA causes a decrease in the stability of the tetrameric molecule with a time course similar to that observed for loss of acetyl‐CoA‐dependent catalytic activity [(1984) FEBS Lett. 127, 157‐160]. The data suggest that the hysteretic responses induced by exposure to EDTA are associated with dissociation of the tetrameric molecule to dimers and monomers having a decreased sensitivity to allosteric activation.
Oxidation of nitroxide radicals by an iron‐hydrogen peroxide‐amino acid system
Authors: Yamaguchi Takeo , Nagatoshi Akiyoshi , Kimoto Eiji
Published: July 2002

The oxidation of nitroxide radicals by the reaction of hemoglobin with hydrogen peroxide occurred using both FeSO4 and amino acids instead of hemoglobin. Tyrosine, phenylalanine, tryptophan, methionine and cysteine in globin were connected with the formation of the oxoammonium cation. Of these amino acids, tyrosine was especially effective in its oxidation. It was found that both the binding of nitroxide radicals to ferric iron and the activation of amino acids by hydroxyl radicals were important in the radical oxidation.
Autoregulation of heat‐shock system in Drosophila Melanogaster
Authors: Evgen'ev Michael B. , Zatsepina Olga L. , Titarenko Helen
Published: July 2002

The cells of the cell‐lethal mutant 1(1)ts403 are characterized by an extremely low level of synthesis of heat‐shock proteins (hsp) after temperature elevation. The mutation affects not only the kinetics of hsp synthesis but also the electrophoretic pattern of hsp. Studies of puffing, RNA and protein synthesis in the mutant strongly suggest that hsp are involved in the regulation of their own synthesis at the level of puff induction, transcription and translation.
Visualization of the hepatic low‐density lipoprotein receptor in rats by sequential scintiscans
Authors: Friedrich E. , Dresel H.A. , Sinn H. , Schettler G.
Published: July 2002

The usefulness of a gamma camera system for external imaging of the degradation sites of low‐density lipoprotein (LDL) is demonstrated in rats. [131I]LDL was injected intravenously in normal rats and rats pretreated with 17α‐ethinyl estradiol for LDL receptor induction. Distribution of the radioligand was followed for 20 min, for perfusion control [131I]albumin was administered. Rats pretreated with 17α‐ethinyl estradiol showed a marked increase in the LDL uptake by the liver, which was not competed by the preinjection of physiological amounts of unlabelled LDL. It is concluded that the injection of small amounts of [131I]LDL is sufficient to image the hepatic LDL receptor and that the endogenous LDL does not compete effectively at physiological LDL levels.
Cooperative and reversible action of three or four hydroxylamine molecules on the water‐oxidizing complex
Authors: Förster Verena , Junge Wolfgang
Published: July 2002

Photosynthetic water oxidation is a four‐step oxidation process which is formally described by the transitions S0 → S1, S1 → S2, S2 → S3, S3 → S4 → S0. In dark‐adapted thylakoids S1 is the most stable and oxygen is liberated after abstraction of three oxidizing equivalents from the water‐oxidizing complex. If hydroxylamine is present at low concentrations (15–100 μM), five instead of three oxidizing equivalents have to be abstracted before dioxygen is liberated. We measured the concentration dependence of this two‐digit shift via the pattern of proton release which is associated with water oxidation. We obtained an apparent Hill coefficient of 2.43. This result could be explained by cooperative binding of 3 or 4 hydroxylamine molecules, and by the assumption that each center which was modified by >= 1 hydroxylamine molecule gave rise to the same modified pattern of proton release.
Histone H5 and Hl° cross‐reacting material is restricted to erythroid cells in chicken
Authors: Shannon M.F. , Wigley P.L. , Wells J.R.E.
Published: July 2002

Monoclonal H5 antibodies and a polyclonal antiserum, raised against the globular domain of chicken H5 (GH5) but which cross‐reacts with histone H1° from mouse liver, were used to search for H5 or H1°‐like proteins in chicken embryo and adult tissue sections by indirect immunofluorescence. Chicken cell lines in culture were examined for H5 protein and H5 mRNA. Histone H5 was detected only in erythroid cells in tissue sections of chicken embryos or adult livers. H5 protein and H5 mRNA were found only in erythroid cells in culture. No cross‐reacting proteins were detected in any other tissue or cell line examined.
Trypsin activation of porcine procolipase
Authors: Wieloch Tadeusz
Published: July 2002

The kinetics of trypsin activation of pancreatic procolipase was investigated and the pH dependence of the binding of procolipase and colipase to a tributyrine‐bile salt interface studied. The K
m was 0.06 mM and K
cat 8 s−1, and was of the same order of magnitude as for the activation of pancreatic zymogens. At basic pH values colipase had a higher affinity for the tributyrine‐bile salt interface as compared to procolipase. The trypsin activation of procolipase ensures a rapid degradation of dietary lipids in the intestine.
Uric acid and allantoin uptake by Bacillus fastidiosus spores
Authors: Salas Jose Antonio , Ellar David J.
Published: July 2002

Uric acid enters Bacillus fasitidiosus spores by a constitutive carrier‐mediated mechanism. The extent of uptake was proportional to the external uric acid concentration up to the limit of solubility. Most of the uric acid taken up after 2 min of incubation was not exchangeable with cold uric acid, suggesting that the uric acid was being quickly metabolized. Allantoin (an uric acid degradation product) was not incorporated by spores unles they were triggered to germinate with uric acid and the induced by allantoin. The induction of this uptake system was inhibited by chloramphenicol. The inability of spores to germinate in the sporulation medium was found to be due to the high pH of the sporulation medium after growth and sporulation.
On the recovery of Cys‐containing peptides during peptide mapping by HPLC
Authors: Koeppe Roger E. , Haw John H. , Paczkowski Jean A.
Published: July 2002

Conditions are presented for separating the major tryptic peptides of E.coli tryptophanyl‐transfer RNA synthetase by reversed‐phase liquid chromatography using a water‐methanol gradient in the presence of 0.1 % trifluoroacetic acid. Three of the peptides contain cysteine and are recovered in good yields if alkylated, but otherwise cannot be detected. A convenient post‐digestion alkylation procedure is appropriate for use with small samples of protein which can be digested under reducing conditions. These results will be of interest for studies of the labeling of sulfhydryl groups in other proteins.
Final steps of the maturation of Omp F, a major protein from the outer membrane of Escherichia coli
Authors: Barbas J.A. , Vázquez D. , Rodríguez-Tébar A.
Published: July 2002

Pulse‐labelling experiments with E. coli cells allowed us to follow the incorporation of de novo proteins into the outer membrane of the cell envelope. Labelled membrane samples containing increasingly different levels of newly synthesized Omp F protein were subjected to chemical cross‐linking with a bifunctional cleavable reagent in order to investigate the process of trimer formation of the protein. From the results obtained, we conclude that the formation of functional Omp F trimers is substantially delayed to, and can be distinguished from, the incorporation of Omp F monomers to the outer membrane.
Differential effect of dichloroacetate on branched‐chain amino acid catabolism in perfused rat hindlimbs
Authors: Schadewaldt Peter , Radeck Wolfgang , Staib Wolfgang
Published: July 2002

Dichloroacetate
Branched‐chain amino acid
Pyruvate
Perfused rat hindlimb
Antibodies to Z DNA stabilized with polyarginine
Authors: Niveleau A. , Roux B. , Adouard V. , Dante R. , Revet B. , Delain E.
Published: July 2002

In the same experimental conditions, hypermethylated B DNA is not recognized by these antibodies.
Structure and biological activity of polysomes stained with Coomassie blue
Authors: Murthy M.R.V. , Hanna N. , Bharucha A.D. , Charbonneau R. , Viallard J.-L. , Dastugue B.
Published: July 2002

Polysomes prestained with Coomassie blue were fractionated on sucrose density gradients giving rise to visible bands corresponding to different size classes of aggregates. Coomassie blue staining enhanced the capacities of brain and liver polysomes to synthesize proteins in vitro, including the synthesis of neuron‐specific enolase. This positive action of the dye was restricted to polysomes and was not manifested when mRNAs isolated from prestained polysomes were tested in in vitro translation or reverse transcription, indicating that the action of the dye consists in stabilization of polysomal structure.
The role of metal ions in the uptake of aspartate aminotransferase and malate dehydrogenase into isolated rat liver mitochondria in vitro
Authors: Passarella S. , Marra E. , Atlante A. , Doonan S. , Quagliariello E.
Published: July 2002

To gain further insight into the mitochondrial receptor area which allows selective uptake of both purified aspartate aminotransferase and malate dehydrogenase into mitochondria, the inhibition of metal complexing agents such as bathophenanthroline and tiron on the uptake of both enzymes has been investigated. In view of the nature of the inhibition found, we propose the existence of metal ion(s) at or near the aspartate aminotransferase, but far from the malate dehydrogenase binding site.
Kinetics of the H+‐ATPase in chromatophores from Rhodospirillum rubrum
Authors: Boork Jeff , Strid Ake , Baltscheffsky Margareta
Published: July 2002

The effect of the electrical potential on the H+‐ATPase of Rhodospirillum rubrum is examined. It is shown that the forward reaction rate (ATP synthesis) is increased by a factor of 10 during illumination while the reversed rate is only slightly decreased. This indicates that the electrical potential across the membrane affects the rate constants mainly by increasing the forward rate constants rather than decreasing the reversed rate constants in order to go from net hydrolysis to net synthesis.
Major transcripts containing B1 and B2 repetitive sequences in cytoplasmic poly(A)+RNA from mouse tissues
Authors: Ryskov Alexei P. , Ivanov Pavel L. , Tokarskaya Olga N. , Kramerov Dmitrii A. , Grigoryan Mariam S. , Georgiev Georgii P.
Published: July 2002

Bl repetitive element
B2 repetitive element
Transcription
Normal mouse tissue
Mouse tumor tissue
Sarcoplasmic reticulum CaATPase: product inhibition suggests an allosteric site for ATP activation
Authors: Coll Richard J. , Murphy Alexander J.
Published: July 2002

Sarcoplasmic reticulum CaATPase hydrolysis of high concentrations of ATP was studied in the presence of ADP. The results obtained were best described as noncompetitive inhibition; added product lowered the V
max but did not affect the slopes of Eadie‐Hofstee plots. At these concentrations (0.5–5 mM), ATP is known to act as both a substrate and as an activator of turnover. The inability of ATP to overcome ADP inhibition suggests that activating ATP binds to an allosteric regulatory site rather than to the phosphorylated active site.
CD spectrum and conformational distribution of cyclotuftsin in solution
Authors: Kataev B.S. , Balodis J.J. , Nikiforovich G.V.
Published: July 2002

CD spectrum calculation
Theoretical conformational analysis
Tuftsin cycloanalog
Peptide conformation
Purification of the enhancing factor from mouse intestines
Authors: Mulherkar Rita , Saraf Anjali , Wagle Archana , Deo M.G.
Published: July 2002

A unique polypeptide, called enhancing factor (EF), which enhances the binding of labeled epidermal growth factor (EGF) to cells, has been isolated. It has been purified to homogeneity from the acid‐soluble proteins of mouse intestines. Earlier, EF was partially purified by two cycles of gel‐permeation chromatography on Bio‐Gel columns. We now report the final purification of EF on high‐performance liquid chromatography (HPLC), using a reverse‐phase column (μBondapak C18). The purity of the protein was confirmed when a single peak was obtained in HPLC. Also, a single protein band was obtained in SDS‐PAGE. Purified EF has the same properties in vitro as those reported earlier for partially purified EF.
Possible incorporation of phosphoserine into globin readthrough protein via bovine opal suppressor phosphoseryl‐tRNA
Authors: Mizutani Takaharu , Tachibana Yoshio
Published: July 2002

Suppressor [32P]phosphoseryl‐tRNA, prepared using bovine seryl‐tRNA synthetase and ATP:seryl‐tRNA phosphotransferase, was mixed with rabbit reticulocyte lysates containing endogenous hemoglobin mRNA having the termination codon UGA (opal). The Chromatographic pattern of the lysate on Sephacryl S‐200 showed that the radioactivity of [32P]Pjphosphate in the hot trichloroacetic acid‐precipitate (phosphoprotein) was eluted at the position between mature hemoglobin and globin subunits. The phosphoprotein, obtained by chromatography on S‐200, moved to the position corresponding to that of globin readthrough protein on SDS‐PAGE. The analyses of the hydrolyzate of the phosphoprotein showed the presence of phosphoserine in the protein. These results suggest that animal opal suppressor tRNA functions in vitro to transfer phosphoserine to the position of the termination codon UGA (opal) on mRNA.
The pyridine nucleotide‐dependent D‐glucose dehydrogenase of Nostoc sp. strain Mac, a cyanobacterium, is subject to thioredoxin modulation
Authors: Juhász A. , Csizmadia V. , Borbély G. , Udvardy J. , Farkas G.L.
Published: July 2002

A pyridine nucleotide‐dependent D‐glucose dehydrogenase (GDH) was isolated and purified about 1000‐fold from Nostoc sp. strain Mac. The activity of this preparation with NADP as cofactor was 2.8‐times that with NAD. This ratio did not change during purification. The enzyme both in crude extracts and after purification proved to be subject to redox modulation. Homologous and heterologous (Anacystics nidulans, Anabaena sp. strain PCC 7120, spinach) thioredoxins, in the presence of 0.5 mM DTT, deactivated the enzyme. The thioredoxin from Nostoc was active with heterologous enzymes: it activated the fructose‐1,6‐bisphosphatase of Anacystis nidulans and the NADP‐dependent malate dehydrogenase of spinach. The thioredoxin‐mediated reduction decreased the apparent V
max value for D‐glucose by about 65% and that for NADP by about 51%. The apparent K
m value for NADP increased upon reduction by about 10‐fold. The apparent K
m value for D‐glucose was but slightly affected by the redox state of the enzyme.
Origin of sequence‐specific recognition of DNA by non‐intercalating anti‐tumor antibiotics
Authors: Mrigank  , Royyuru A.K. , Kothekar V.
Published: July 2002

Partitioning of energy in the interaction of non‐intercalating antibiotics (netropsin, netropsin without its cationic ends and two analogs of distamycin A) with different base sequences of B‐DNA is studied here by the atom‐atom potential technique and geometry optimization procedures. The results show that electrostatic forces contribute substantially to the stabilization energy as well as to the sequence specificity. The hydrogen‐bonding term is also sequence specific and is significant in properly orienting the drug molecule. Relative roles of the hydrogen bonding and electrostatic interactions depend on the dielectric property of the medium.
Antibody‐coated liposomes
Authors: Senior Judith , Waters J.A. , Gregoriadis Gregory
Published: July 2002

Incubation of small unilamellar liposomes composed ofequimolar phospholipid and cholesterol with mouse IgG or mouse monoclonal IgG1 for up to 24 h resulted in considerable (34‐89%) adsorption of the protein onto the liposomal surface. Immunoglobulin remained adsorbed after exposure to mouse plasma and, in the case of monoclonal (anti‐HBSAg) IgG1, was able to mediate association of the liposomes with the antigen. Extensive immunoglobulin adsorption suggests caution in interpreting co valent linkage values obtained upon prolonged incubation of chemically modified antibodies with liposomes. It may also be a preferred alternative in preparring targeted liposomes for intravenous use when chemically modified antibodies promote premature clearance of the antibody‐liposome complex from the circulation.
Heteroduplex stabilities in highly repetitive DNA
Authors: Dodin Guy
Published: July 2002

Codon repeats encountered in DNA sequences may formally lead to several double‐stranded structures of similar stabilities. This is observed in the highly repetitive sequences of some Plasmodium antigens (S‐antigen, CS proteins). It is postulated that gene recombination may occur via various heteroduplex molecules thus leading to antigenic polymorphism of Plasmodium parasites.
Action of imidazole derivatives on oxidation of unsaturated fatty acids by soybean lipoxygenase
Authors: Beneytout Jean Louis , Brunaud Annie , Tixier Marie
Published: July 2002

The effects of imidazole derivatives on the oxidation of linoleic (or arachidonic) acid by soybean lipoxygenase was studied. Carbimazole (at the concentrations employed) was found to have an effect on the reaction. The initial reaction velocity, the maximum velocity and the affinity constant were all modified. These results suggest that carbimazole exerts actions both on the affinity of the enzyme for the substrate and on the final product of the reaction. Carbimazole has the highest electron donating potential and, at the doses used, was the most active of the three compounds tested. The other derivatives were found to have similar but much slower actions on enzyme activity. Such compounds, which are often used in thyroid disorders, could also act on polyunsaturated fatty acid metabolism and so could provoke secondary effects.
Amino‐terminal heterogeneity of E. coli TEM‐β‐lactamase secreted from Bacillus subtilis
Authors: Kalkkinen Nisse , Sibakov Mervi , Sarvas Matti , Palva Ilkka , Kääriäinen Leevi
Published: July 2002

E.coli TEM‐β‐lactamase, secreted from Bacillus subtilis after transformation with three different hybrid plasmids, was purified and subjected to direct amino‐terminal sequence analysis. The results show that the signal sequence cleavage site varies depending on the hybrid plasmid construction and cannot be exactly predicted from the DNA sequences. The results are of general interest if recombinant DNA technology is used to synthesize, e.g. pharmaceutical products where the preservation of the authentic amino‐terminal structure is highly desirable.
Predicted sequence of the host‐protective immunogen of infectious bursal disease virus
Authors: Hudson Peter J. , McKern Neil M. , Fahey Kevin J. , Azad Ahmed A.
Published: July 2002

The genome of Australian strain 002‐73 of infectious bursal disease virus (IBDV) has been cloned as cDNA fragments into an expression library based on pUR plasmid vectors. Recombinant colonies were selected with a monoclonal antibody specific for the 32‐kDa host‐protective immunogen of IBDV and fully characterized by nucleotide sequence analysis. The amino acid sequence of several tryptic peptides derived from the native 32‐kDa structural protein has confirmed the coding region assignment and nucleotide sequence data. We believe this to be the first published sequence of a birnavirus‐encoded protein and these data may provide the basis for an effective subunit vaccine against IBDV
Cross‐reactivity studies on the interaction between elongation factors Tu and Ts from Streptomyces aureofaciens and Escherichia coli in the GDP exchange reaction
Authors: Weiser Jaroslav , Ruusala Tarmo
Published: July 2002

The method of purification of elongation factor Ts from Streptomyces aureofaciens is described. Purified elongation factors Ts from S. aureofaciens and Escherichia coli were tested in cross‐reactivity studies with elongation factors Tu from both species in a GDP exchange reaction under equilibrium and non‐equilibrium conditions. Experiments have revealed that slower spontaneous release of GDP from S. aureofaciens EF‐Tu is compensated for by higher affinity of homologous EF‐Ts towards EF‐Tu and thus the initial rates of EF‐Ts catalysed GDP exchange can be kept the same in both E. coli and S. aurefaciens in vitro systems.
A single chloroplast protein with latent activities of both N ADPH‐dependent glyceraldehyde‐3‐phosphate dehydrogenase and phosphoribulokinase
Authors: Nicholson Sylvia , Easterby John S. , Powls Roy
Published: July 2002

An algal chloroplast protein possessing latent NADPH‐dependent glyceraldehyde‐3‐phosphate dehydrogenase and latent phosphoribulokinase activities has been purified. Both activities were stimulated by incubation with dithiothreitol and NADPH. The protein had subunit composition 8G6R and on activation depolymerized to discrete NADPH‐dependent glyceraldehyde‐3‐phosphate dehydrogenase (4G) and phosphoribulokinase (2R). Similar depolymerization promoted by reduced thioredoxin could account for light‐dependent activations of phosphoribulokinase and NADPH‐dependent glyceraldehyde‐3‐phosphate dehydrogenase observed in algae and higher plants.
Requirement of monohydroperoxy fatty acids for the oxygenation of 15Ls‐HETE by reticulocyte lipoxygenase
Authors: Kühn H. , Wiesner R. , Stender H. , Schewe T. , Lankin V.Z. , Nekrasov A. , Rapoport S.M.
Published: July 2002

The lipoxygenase from reticulocytes oxygenates 15Ls‐HETE to 8‐hydroperoxy‐15‐hydroxy‐5,9,ll,13‐eicosatetraenoic acid and 5‐hydroperoxy‐15‐hydroxy‐6,8,11,13‐eicosatetraenoic acid only in the presence of catalytic concentrations of monohydroperoxy fatty acids. During this reaction the hydroperoxy fatty acids are converted to more polar products including hydroxy fatty acids. From kinetic measurements of 15LsHETE oxygenation it was calculated that 1 mol monohydroperoxy fatty acid is consumed during the oxygenation of about 9 mol 15Ls‐HETE.
Temperature effects on solutions of vinblastine‐induced polymers assembled from brine shrimp (Anemia) tubulin
Authors: MacKinlay S.A. , Ludueña R.F. , MacRae T.H.
Published: July 2002

Purified Artemia tubulin in the presence of neural microtubule‐associated proteins and vinblastine, or with vinblastine alone, forms extensive coils. Reduction in temperature of a coil‐containing solution to 4°C causes an increase in turbidity, which returns to previous levels once the solution is warmed. Examination of negatively stained samples indicates that the turbidity fluctuations are not accompanied by a pronounced change in coil structure nor by increased polymer formation. Bovine neural tubulin responds in the same way as Artemia tubulin to vinblastine and temperature. An interesting novel response to vinblastine, shared by tubulins from phylogenetically distinct organisms, is illustrated by our results.
Stimulation of progesterone synthesis, in corpus luteum cells isolated from 4‐amino‐3,4‐d‐pyrazolopyrimidinetreated rats, by cholesterol presented in non‐lipoprotein form
Authors: Petrou Christos , Booth Roger , Stansfield David A.
Published: July 2002

We have previously shown that the administration of 4‐amino‐3,4‐d‐pyrazolopyrimidine (4‐APP) to rats reduces progesterone synthesis by cells subsequently isolated from their corpora lutea, and that plasma high density lipoprotein (HDL) can restore this progesterone synthesis to normal. In this paper we demonstrate that a dispersion of phospholipid and cholesterol, but not other sterols, can enhance this 4‐APP‐disabled progesterone synthesis to the same level as can HDL, thus providing the first direct evidence that cholesterol is the component of HDL upon which rat corpus luteum depends for its ability to synthesize progesterone.
The effects of phospholipase C on the voltage‐gated Ca current in Lymnaea stagnalis mollusc neurons
Authors: Akopyan Abraham R. , Chemeris Nikolai K. , Iljin Victor I. , Ilyasov Fuat E. , Selishcheva Alevtina A.
Published: July 2002

Application of phospholipase C to isolated voltage‐clamped molluscan neurons substantially increased the voltage‐gated Ca current (I
ca) in most of the cells studied. In contrast, phosphoinositide‐specific phospholipase C inhibited I
ca in all neurons. The mechanism of phospholipase C‐induced alterations of I
ca is poorly understood at present, but they may have some relevance to plasma membrane phosphoinositide‐coupled changes in cytosolic Ca2+ and to α‐adrenergic neurotransmitter control of neuronal I
ca.
Luminescence decay kinetics in relation to the relaxation of the transthylakoid ΔpH from high and low CO2 adapted cells of Scenedesmus obliquus
Authors: Sundblad Lars-Göran , Palmqvist Kristin , Samuelsson Göran
Published: July 2002

Luminescence decay kinetics was shown to be polyphasic with two relative maxima observed, when high CO2 adapted cells of Scenedesmus obliquus were stressed by CO2 deficiency. Low CO2 adapted cells exhibited a single maximum. Luminescence from high CO2 adapted cells under high CO2 conditions decayed asymptotically without maxima. The magnitude of the transthylakoid ΔpH was shown to be related to the intensity of luminescence in an antiparallel way. The relaxation kinetics of the ‐ΔpH was shown to be complex, with an interval of increasing or maintained ΔpH. A working hypothesis is presented in order to explain polyphasic luminescence decay kinetics in terms of luminescence quenching by the transthylakoid ΔpH.
Accessibility of phosphodiester bonds in the yeast ribosomal 5 S RNA protein complex
Authors: McDougall John , Nazar Ross N.
Published: July 2002

The tertiary structure of the protein‐associated yeast ribosomal 5 S RNA was examined using ethylnitrosourea reactivity as a probe for phosphodiester bonds. A reduced reactivity was consistently observed in at least nine residues within four distinct regions of the RNA sequence. Seven of these were also observed in three regions of the free RNA molecule while two, A27 and G30, were only present in the ribonucleoprotein complex. The results strongly suggest that the tertiary structure of the free eukaryotic 5 S RNA is largely conserved in the 5 S RNA‐protein complex although it appears to be further stabilized in interaction with the ribosomal protein.
Chromatin superstructure
Authors: Dimitrov S.I. , Apostolova T.M. , Makarov V.L. , Pashev I.G.
Published: July 2002

Hen erythrocyte chromatin was treated with trypsin immobilized on collagen membranes and the unfolding of chromatin fiber was followed by light scattering at 90° and flow linear dichroism. Chromatin was found almost completely decondensed when the bulk of H1 and H5 was digested while H3 was still intact. Further digestion leading to degradation of both H3 and the rest of H1 and H5 accounted for no more than 10–15% of the total effect. When chromatin with trypsin‐cleaved H1 and H5 was titrated with increasing amounts of spermidine it folded similarly to the control sample. This finding suggests that charge neutralization appears a likely mechanism for maintaining the structure of the 30 nm chromatin fiber by the C‐terminal domain of H1 and H5.
Photochemical cross‐linking of 125I‐hydroxyphenylisopropyl adenosine to the A1 adenosine receptor of rat adipocytes
Authors: Green Allan , Stuart Charles A. , Pietrzyk Robert A. , Partin Maristella
Published: July 2002

Rat adipocyte plasma membranes were incubated with the A1 adenosine receptor agonist, 125I‐hydroxyphenylisopropyl adenosine (1 nM) and then treated with the photoactive cross‐linking agent, ANB‐NOS. The membranes were solubilized and analyzed by SDS‐PAGE and autoradiography. A single protein, M
r approx. 38 000, was specifically labeled. Reduction with 2‐mercaptoethanol did not affect the apparent M
r of the labeled protein. Labeling was inhibited by the adenosine receptor agonists, HPIA, PIA and NECA, and by the antagonist, theophylline, but was unaffected by inosine. We conclude that the A1 adenosine receptor is a single protein of M
r approx. 38 000.
An EPR study of Signal II in oriented photosystem II membranes
Authors: Brok Martin , Horikx Johannes T.G. , Hoff Arnold J.
Published: July 2002

Signal II
EPR
Orientation
Hyperfine coupling
Fecal excretion of intestinal glycosphingolipids by newborns and young children
Authors: Larson Göran , Watsfeldt Peter , Falk Per , Leffler Hakon , Koprowski Hilary
Published: July 2002

Glycosphingolipids were shown to persist in human fecal excretions from birth up 2 years of age. The pattern of glycosphingolipids was dependent on blood group and secretor status of the child and changed dramatically during the first months of life. Perinatally cerebroside, hematoside and blood group active fucolipids were dominating among fecal glycolipids. From the time of weaning lactosylceramide abruptly became and then persisted as a dominating glycolipid although cerebroside, complex gangliosides and blood group active fucolipids could still be detected in feces even at 2 years of age.
Disulfide bonds within the α‐subunit of insulin receptors in rat liver and brain membranes
Authors: Nagao Munehiko , Sakamoto Choitsu , Matozaki Takashi , Baba Shigeaki
Published: July 2002

We have characterized inter‐ and intrasubunit disulfide bonds of insulin receptors using reductant‐treated rat liver and brain membranes. In autoradiograms of 125I‐insulin cross‐linked to both membranes pretreated with dithiothreitol, the intensity of affinity‐labeled bands of the αβ‐heterodimer and α‐subunit was increased. Interestingly, labeled 120 and 110 kDa bands considered to be the α‐subunit in partially reduced liver and brain membranes moved to 130 and 120 kDa bands under further reduced conditions, respectively. Double electrophoresis of each partially reduced band in the presence of reductants clearly demonstrates that the α‐subunit of insulin receptors contains intrasubunit disulfide bonds.
Neutrophil specific 33 kDa protein: Its Ca2+‐ and phospholipid‐dependent intracellular translocation
Authors: Sato Eisuke F. , Morimoto Yasuko M. , Matsuno Tsuyoshi , Miyahara Masanobu , Utsumi Kozo
Published: July 2002

A 33 kDa protein from neutrophils has been shown to associate reversibly with phosphatidylserine containing liposomes in a Ca2+‐dependent manner. The protein was purified from guinea pig neutrophils. Immunoblotting and cytochemical studies with polyclonal and monoclonal antibodies to the protein revealed that the protein is commonly distributed in neutrophil cytoplasm of different animal species. The protein was translocated to the plasma membrane by treatment with stimuli. Thus the 33 kDa protein is neutrophil specific and may be involved in transmembrane signaling.
A microtechnique for quantification of detergent‐solubilized muscarinic and nicotinic acetylcholine receptors using a semi‐automated cell harvester
Authors: Ahmad Ateeq , Gordon Richard K. , Chiang Peter K.
Published: July 2002

A specific method for the rapid assay of muscarinic acetylcholine receptors (mAChR), either detergent‐solubilized or in neuroblastoma cells, is described. This method is also applicable to the assay of nicotinic acetylcholine receptors. The procedure employs a cell harvester and microtiter plates, and has the advantage of requiring small quantities of radioligand, microgram quantities of detergent‐solubilized cholinergic receptor or less cells. The binding parameters such as the equilibrium dissociation constants (K
d) of mAChR and nicotinic acetylcholine receptor (nAChR) and inhibition constants (K
i) for antagonists determined by the present method are in excellent agreement with values determined by other methods. This assay procedure for mAChR and nAChR should facilitate the rapid screening of cholinergic agonists/antagonists and also the further purification and characterization of mAChR.