bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic AMP is involved in sexual reproduction of Chlamydomonas eugametos
Authors: Pijst H.L.A. , van Driel R. , Janssens P.M.W. , Musgrave A. , van den Ende H.
Published: July 2002

When plus and minus mating type gametes of Chlamydomonas eugametos were mixed, a rapid transient increase in the amount of cAMP was observed with a maximum at 20 s after the start of the sexual agglutination reaction. The transient increase only occurred within the cells and was also exhibited when cell suspensions of single mating type were presented with isolated flagella of the other mating type. Cyclic AMP‐dependent protein kinase and cyclic AMP‐phosphodiesterase activities were found in cell homogenates. Since the rise in cAMP concentration preceded all known morphological and physiological changes in the cells that prepare them for fusion, it might be a primary response, induced by sexual agglutination.
Malonyl CoA inhibition of carnitine palmityltransferase in rat heart mitochondria
Authors: Paulson Dennis J. , Ward Karen M. , Shug Austin L.
Published: July 2002

The effects ofmalonyl CoA on carnitine palmityltransferase I (CPT‐I), fatty acid‐supported state 3 respiration, and carnitine reversal of palmityl CoA inhibition of state 3 respiration and of the adenine nucleotide translocator, were studied in isolated rat heart mitochondria. Malonyl CoA was a potent competitive inhibitor of CPT‐I with an I
50 of 0.8 μM. Fasting did not affect CPT‐I activity or the I
50 value of malonyl CoA. Malonyl CoA inhibited fatty acid‐supported respiration and prevented carnitine from reversing the inhibition of the adenine nucleotide translocator by palmityl CoA. These findings suggest that malonyl CoA may affect fatty acid oxidation in the heart.
Alterations in enzyme expression on 12‐O‐tetradecanoylphorbol‐13‐acetate‐induced differentiation of chronic lymphocytic leukemia cells
Authors: Srivastava B.I.Sahai , Tin Han
Published: July 2002

Several enzyme activities were examined to establish a relationship between their expression and terminal differentiation of B‐chronic lymphocytic leukemia (CLL) cells to plasma cells by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA). Although adenosine deaminase activity did not change significantly, thymidine phosphorylase and purine nucleoside phosphorylase increased 2–3‐fold on TPA‐induced differentiation of CLL cells. In addition, cytochemical reactions for non‐specific esterase and acid phosphatase changed from very weak to intense on differentiation of CLL cells to plasma cells. The above markers, particularly cytochemical, could be useful for the classification of B‐cell malignancies and for studying B‐cell differentiation.
Valosin: isolation and characterization of a novel peptide from porcine intestine
Authors: Schmidt Wolfgang E. , Mutt Viktor , Carlquist Mats , Kratzin Hartmut , Conlon J.Michael , Creutzfeldt Werner
Published: July 2002

It does not show structural homology to known protein or nucleotide sequences. According to preliminary experiments, valosin possesses biological effects on the gastrointestinal tract of the dog.
Citric acid cycle enzymes of the archaebacteria: citrate synthase and succinate thiokinase
Authors: Danson Michael J. , Black Susan C. , Woodland David L. , Wood Pauline A.
Published: July 2002

In eubacteria and eukaryotes, citrate synthase and succinate thiokinase exhibit a species‐dependent diversity of structure, activity and regulation. These enzymes have now been examined in the archaebacteria and it is found that each of the three major subgroups, the extreme halophiles, the thermoacidophiles and the methanogens, possesses characteristic types of citrate synthase and succinate thiokinase. The observed patterns of structure and regulation of these two enzymes are compared across the three evolutionary lineages.
Synexin binds in a calcium‐dependent fashion to oriented chromaffin cell plasma membranes
Authors: Scott Janet H. , Creutz Carl E. , Pollard Harvey B. , Ornberg Richard
Published: July 2002

Oriented plasma membrane fragments from chromaffin cells, isolated on polylysine‐coated polyacrylamide beads, bind synexin in a calcium dependent manner. Synexin binding was also detected on beads coated with chromaffin granule membranes, but not to beads coated with erythrocyte membranes or to uncoated beads. Synexin binding to plasma membrane coated beads showed a specific requirement for calcium (K
12 = 200 μM) and was insensitive to other divalent cations such as magnesium, strontium and barium. Synexin binding to either plasma membrane or granule membrane coated beads was saturable, was partially reversible by EGTA and was directly observed by SDS‐polyacrylamide gel electrophoresis.
Dephosphorylation suppresses the activity of neurofilament to promote tubulin polymerization
Authors: Minami Yasufumi , Sakai Hikoichi
Published: July 2002

The phosphate content of neurofilament was diminished by half, from 49.4 to 22.9 , by treatment with alkaline phosphatase. Dephosphorylation decreased the activity of neurofilament to promote tubulin assembly. This suppression was supposed to be mainly due to dephosphorylation of the 200 kDa subunit of neurofilament. Dephosphorylation of the isolated 200 kDa subunit caused suppression of its activity to promote tubulin polymerization. These results suggest that changes in the phosphate content modulate interaction of neurofilament with tubulin.
Interaction of bovine seminalplasmin with Escherichia coli RNA polymerase in the presence of rifampicin
Authors: Sitaram N. , Chatterji D.
Published: July 2002

RNA polymerase
Inhibitor
Seminalplasmin
Rifampicin
Fluorescence
Patch‐clamp studies of ion transport in isolated plant vacuoles
Authors: Hedrich R. , Flügge U.I. , Fernandez J.M.
Published: July 2002

Plant cell vacuoles act as storage depots for substances such as sugars, organic and inorganic ions, many of which are commercially important. We have used the patch‐clamp technique to characterize an ATP‐dependent proton pump and a non‐selective channel in the vacuolar membrane in single isolated barley leaf vacuoles. The large (60 to 80 pS) ion channel shows inward rectification, and carries both K+ or malate ions driven by their concentration gradient as well as the electrical gradient established by the ATP‐dependent proton pump.
Mitotic inhibitors arrest the growth of Plasmodium falciparum
Authors: Usanga E.A. , O'Brien Estella , Luzzato L.
Published: July 2002

We report that the mitotic inhibitor, vinblastin (VLB), is highly toxic to the malarial parasite, Plasmodium falciparum. In cultures in vitro growth is inhibited by 50% at a VLB level of about 28 nM, and totally abolished at a level of 100 nM. By tests on synchronized cultures we have found that the effect of VLB takes place at the trophozoite stage. Colcemid also inhibits schizogony with somewhat different kinetics. By mutagenesis with nitrosoguanidine followed by VLB selection we have isolated a VLB‐resistant mutant which exhibits cross‐resistance to vincristine. These data suggest a critical role of microtubules in the asexual schizogonic cycle of P. falciparum.
Polyethylene glycol‐stimulated microsomal GTP hydrolysis
Authors: Nicchitta Christopher V. , Joseph Suresh K. , Williamson John R.
Published: July 2002

It has recently been observed that GTP mediates Ca2+ release from internal Ca2+ stores. In contrast to effects on permeabilized cells, GTP‐dependent Ca2+ release in isolated microsomes requires the presence of polyethylene glycol (PEG). We have investigated the effects of PEG on microsomal GTPase activity and report that PEG stimulates a high‐affinity (K
m = 0.9 μM) GTPase. The effects of PEG reflect an increase in the V
max of this activity; no effects on K
m were observed. The concentration dependence for PEG‐dependent stimulation of the high‐affinity GTPase exactly mimicked that for GTP‐dependent Ca2+ release. The stimulation of GTP hydrolysis by PEG was specific for the microsome fraction; only small effects were obtained with plasma membrane or cytosol fractions. As observed for GTP‐dependent Ca2+ release, the microsomal PEG‐stimulated GTPase was competitively inhibited by the GTP analog GTPγS (K
i = 60 nM). It is proposed that the PEG‐stimulated GTPase may represent an intrinsic activity of the guanine nucleotide binding protein involved in the regulation of reticular Ca2+fluxes.
Saturable binding of thyroid hormone to isolated rat hepatocytes
Authors: Blondeau Jean-Paul
Published: July 2002

The binding of [125I]triiodothyronine (T3) to freshly prepared rat hepatocytes was studied at 0°C. The abundant non‐saturable binding could be suppressed by washing the cells with alkaline buffer, pH 10.5 at 0° C, without loss of cell viability, thus allowing detection of saturable binding. Three classes of binding sites were indentified from analysis of the sautrable T3 binding in the presence and absense of bromosulfophthalein (BSP). One of these classes was inhibited by BSP. The T3 dissociation constants were 3.5, 35 and 115 nM and the number of sites was respectively 0.9, 20 and 36 × 106 sites/cell. L‐T3 had a 10‐times higher affinity than D‐T3 and a 50‐times higher affinity than triiodothyroacetic acid. Saturable T3 binding was associated with plasma membrane‐containing subcellular fractions. These binding sites may be related to those previously described in isolated plasma membranes from rat liver and could be involved in the entry of T3 into the hepatocyte.
Near‐infrared‐excitation resonance Raman spectra of bacterial photosynthetic reaction centers Implications for path‐specific electron transfer
Authors: Bocian David F. , Boldt Nancy J. , Chadwick Barry W. , Frank Harry A.
Published: July 2002

The first near‐infrared (Qy)‐excitation resonance Raman spectrum of photosynthetic reaction centers (Rb. sphaeroides wild type) is reported. This spectrum exhibits features which are not observed with excitation into either the Qx or Soret absorption bands. The spectral data indicate that the partial double‐bond character is induced in the C9C10 bond of the isocyclic ring of one of the pigments via interactions with the protein. It is proposed that this modified pigment is the L‐subunit bacteriopheophytin and that the preference for electron transfer to this molecule could be in part due to the change in electronic structure induced by the site‐specific pigment‐protein interaction.
How to determine the efficiency of intermediate transfer in an interacting enzyme system?
Authors: Tompa Péter , Batke József , Ovádi Judit
Published: July 2002

A kinetic method, based upon measuring the transient time of coupled reactions, is proposed for the determination of the intermediate channel efficiency in a system of functionally interacting enzymes. The procedure rests upon a novel description in which the transient time is expressed as a function of channel efficiency and lifetime of the intermediate molecules. By this approach the reduction of transient time can be explained even if no changes in the kinetic parameters of the individual reactions occur. For determining channel efficiency, a linearized form has been evaluated and applied to the analysis of the kinetics of the aspartate aminotransferase‐glutamate dehydrogenase coupled reaction, for which the data were taken from the literature [(1982) Eur. J. Biochem. 121, 511–517].
Ile‐Ser‐bradykinin (T‐kinin) and Met‐Ile‐Ser‐bradykinin (Met‐T‐kinin) are released from T‐kininogen by an acid proteinase of granulomatous tissues in rats
Authors: Sakamoto Wataru , Satoh Fumihiko , Gotoh Katsuhiro , Uehara Soichiro
Published: July 2002

An acid proteinase of granulomatous tissues in rats with carrageenin‐induced inflammation released kinin from T‐kininogen. The kinin isolated by n‐butanol extraction was separated by reverse‐phase high‐performance liquid chromatography into T‐kinin and a T‐kinin derivative. From determination of its amino acid composition and its immunoreactivity toward anti‐bradykinin antiserum, the T‐kinin derivative was identified as Met‐Ile‐Ser‐bradykinin (Met‐T‐kinin).
Identification and characterization of a glutamate dehydrogenase in the unicellular cyanobacterium Synechocystis PCC 6803
Authors: Florencio F.J. , Marqués S. , Candau P.
Published: July 2002

Glutamate dehydrogenase activity has been detected in permeabilized cells of the unicellular cyanobacterium Synechocystis PCC 6803 at similar levels to those of glutamate synthase. The enzyme responsible has been purified by affinity chromatography on 2′,5′‐ADP‐Sepharose and identified as an NADPH‐specific glutamate dehydrogenase. The enzyme catalyzes preferentially glutamate formation rather than the reverse reaction, with K
m values for NADPH, 2‐oxoglutarate and ammonia of 20 μM, 1.5 mM and 3.7 mM, respectively. It is composed of four identical subunits giving a total molecular mass of 208 kDa for the native protein. Its physiological role is discussed in terms of being an alternative pathway to the glutamine synthetase‐glutamate synthase cycle for ammonia assimilation.
Secretion of 5‐hydroxytryptamine from electropermeabilised human platelets Effects of GTP and cyclic 3′, 5′‐AMP
Authors: Knight D.E. , Scrutton M.C.
Published: July 2002

Enhancement by thrombin of Ca2+ ‐dependent 5HT secretion in the absence of added GTP decreases as the time between electropermeabilisation and addition of thrombin is increased. No decrease occurs if thrombin is added with GTP. Observation of apparent GTP‐independent receptor/phospholipase C coupling may result from the presence of bound GTP in the preparation. Enhancement by GTP of Ca2+ ‐dependent 5HT secretion occurs with a significant lag indicating an agonist‐independent effect. Cyclic 3′,5′‐AMP inhibits enhancement by GTP of Ca2+ ‐dependent 5HT secretion while having no effect on enhancement induced by GTPγS. Hence cyclic AMP may impair receptor/phospholipase C coupling by enhancing Np GTPase activity.
Neurotrophic effect of naturally occurring long‐chain fatty alcohols on cultured CNS neurons
Authors: Borg J. , Toazara J. , Hietter H. , Henry M. , Schmit G. , Luu B.
Published: July 2002

A long‐chain fatty alcochol,n‐hexacosanol, that we have isolated from the Far‐Eastern traditional medicinal plant, Hygrophila erecta, Hochr., is shown to promote the maturation of central neurons. Added at 500 nM to fetal rat brain neurons in culture, it increased both neurite outgrowth by a factor of 4–6 and the number of collaterals, especially in multipolar neurons. The biochemical differentiation of cultured neurons was also strikingly enhanced by this compound: it increased the protein content and almost doubled the activities of two neuron‐specific enzymes, phosphate‐activated glutaminase and neuron‐specific enolase, by 92 and 78%, respectively. Extensive studies with several synthetic long‐chain fatty alcohols showed that the neurotrophic activity was maximal for n‐hexacosanol. It is suggested that some long‐chain fatty alcohols with an appropriate length of hydrocarbon chain might play an important role in central neuron development.
Proline residues in the maturation and degradation of peptide hormones and neuropeptides
Authors: Mentlein Rolf
Published: July 2002

The proteases involved in the maturation of regulatory peptides like those of broader specificity normally fail to cleave peptide bonds linked to the cyclic amino acid proline. This generates several mature peptides with N‐terminal X‐Prosequences. However, in certain non‐mammalian tissues repetitive pre‐sequences of this type are removed by specialized dipeptidyl (amino)peptidases during maturation. In mammals, proline‐specific proteases are not involved in the biosynthesis of regulatory peptides, but due to their unique specificity they could play an important role in the degradation of them. Evidence exists that dipeptidyl (amino)peptidase IV at the cell surface of endothelial cells sequesters circulating peptide hormones which are then susceptible to broader aminopeptidase attack. The cleavage of several neuropeptides by prolyl endopeptidase has been demonstrated in vitro, but its role in the brain is questionable since the precise localization of the protease is not clarified.
Glycoprotein nature of α2‐adrenergic receptors labeled with p‐azido[3H] clonidine in calf retina membranes
Authors: Convents André , De Backer Jean-Paul , Van Driessche Edilbert , Convents Daniel , Beeckmans Sonia , Vauquelin Georges
Published: July 2002

α2,‐Adrenergic receptors in calf retina membranes can be specifically labeled with the tritiated agonist p‐azido[3H]clonidine. Saturation binding in the dark occurs with high affinity (1.3 ± 0.3 nM) to a single class of sites (1122 ± 67 fmol/mg protein). Irradiation of the membrane‐bound radioligand results in the labeling of a peptide band with an apparent size of 65 kDa and a characteristic pharmacological profile for an α2‐adrenergic receptor. The carbohydrate moieties of the α2‐receptor are characterized by lectin affinity chromatography and glycosidase treatment. The Nonidet P‐40‐solubilized, p‐azido[3H]clonidine‐labeled receptors are completely retained by Con A‐ as well as WGA‐Sepharose columns. Neuraminidase, α‐mannosidase and TFMS do not affect the electrophoretic mobility of the receptor on SDS‐PAGE whereas endoglycosidase F reduces the apparent size to 45 kDa.
Evidence for a membrane‐bound pyrophosphatase in Dictyostelium discoideum
Authors: MacDonald James I.S. , Weeks Gerald
Published: July 2002

Plasma membrane enriched fractions of Dictyostelium discoideum contain a Des‐insensitive ATPase activity that can be fractionated by DEAE‐Sephacel into a major vanadate‐sensitive activity and a minor vanadate‐insensitive activity. The vanadate‐insensitive activity hydrolysed pyrophosphate considerably more rapidly than ATP or any other substrate tested, and the enzyme was therefore designated a pyrophosphatase. The enzyme had no activity on AMP or p‐nitrophenyl phosphate. The pyrophosphatase activity was maximal at alkaline pH values and stimulated by Mg2+ but not by Ca2+, properties of the enzyme that are very similar to those of the previously characterized pyrophosphatases of the plant tonoplast membrane. The pyrophosphatase activity of total membrane extracts changed very little during Dictyostelium differentiation.
Functional characterization of Asp‐317 mutant of human renin expressed in COS cells
Authors: Yamauchi Takeshi , Nagahama Masami , Hori Hitoshi , Murakami Kazuo
Published: July 2002

Renin is an unique aspartyl (acid) protease with optimal activity at neutral pH. It has been suggested that Ala‐317 of human renin contributes to neutral optimum pH of the enzyme [(1984) FEBS Lett. 174, 102–111]. The hypothesis was verified by the characterization of mutant renin in which Ala‐317 was replaced with Asp by a site‐directed mutagenesis. Wild‐type and mutant renins, which were expressed in COS cells, exhibited different pH‐activity profiles and optimum pH of the mutant enzyme was lower than that of the wild‐type enzyme. This result suggests that Ala‐317 of human renin plays an important role in the determination of optimum pH of the enzyme.
Membrane action of synthetic N‐terminal peptides of influenza virus hemagglutinin and its mutants
Authors: Düzgüneş Nejat , Gambale Franco
Published: July 2002

Synthetic peptides corresponding to the N‐terminal of the cleaved hemagglutinin (HA2) of influenza virus induce an increase in conductance of planar phospholipid bilayers, and cause the release of encapsulated molecules from large unilamellar liposomes. Two mutant peptides, derived from hemagglutinins of mutant viruses with no or reduced fusion activity, do not alter the membrane conductance significantly. These observations support the hypothesis that influenza virus fuses with its target membrane by inserting the HA2 N‐terminal into the membrane.
Amino acid sequence template useful for α‐helix‐turn‐α‐helix prediction
Authors: Shestopalov Boris V.
Published: July 2002

Necessary stereochemical requirements for an amino acid sequence segment to fold into an α‐helix‐turn‐α‐helix supersecondary structure are presented in sequence template form. The usefulness of the template is illustrated by α‐helix‐turn‐α‐helix predictions consistent with experimental data from the large T antigens of two polyoma viruses, simian virus 40 (segment 143–165) and mouse polyoma virus (segment 297–319), and the yeast transcription activator GCN4 (segment 256–278).
Prothymosin α is a nuclear protein
Authors: Gómez-Márquez Jaime , Segade Fernando
Published: July 2002

Prothymosin α, a protein first isolated from rat thymus and widely distributed in animal tissues, has an attributed role in the stimulation of the immune system. Its structure contains thymosin α1, a Glu‐rich domain and a putative nuclear location signal. Furthermore, the amount of this protein seems to be associated with the relative size of the nucleus and is inducible during cell growth. We postulate that prothymosin α is located inside the cell nucleus and that its activity might be to organize some protein complexes.
Specificity of GDP‐Man:dolichyl‐phosphate mannosyltransferase for the guanosine diphosphate esters of mannose analogues containing deoxy and deoxyfluoro substituents
Authors: McDowell William , Schwarz Ralph T.
Published: July 2002

Guanosine diphosphate (GDP) esters of 2‐deoxy‐D‐glucose (2dGlc), 2‐deoxy‐2‐fluoro‐D‐mannose (2FMan), 3‐deoxy‐D‐mannose (3dMan), 4‐deoxy‐D‐mannose (4dMan) and 6‐deoxy‐D‐mannose (6dMan) have been synthesised and tested for their ability to act as inhibitors of dolichyl phosphate mannose synthesis (enzyme: GDP‐mannose:dolichyl‐phosphate mannosyltransferase, EC 2.4.1.83) in chick embryo cell microsomal membranes. The following order of efficiency was found with the apparent K
i in parentheses: GDP‐6dMan (0.40 μM±0.15) > GDP‐3dMan (1.0 μM±0.1) = GDP‐2dGlc (1.3 μM±0.2) > GDP‐4dMan (3.1 μM±0.1) GDP‐2FMan (15 μM±0). For comparison the K
m for GDP‐Man was 0.52 μM±0.02 and the K
i for GDP was 56 μM±2. These results indicate that the 6‐hydroxyl group of mannose is not crucial for emzyme‐substrate recognition, whereas the 2‐ and 3‐hydroxyls may have some involvement. The 4‐hydroxyl appears to be an important determinant for enzyme‐substrate recognition in this mannosyltransferase.
Electron transfer in the isolated photosystem II reaction centre complex
Authors: Nugent Jonathan H.A. , Telfer Alison , Demetriou Christalla , Barber James
Published: July 2002

We have characterised the electron‐transfer properties of the D1/D2/cytochrome b‐559 complex using EPR spectrometry. The complex can transfer electrons to silicomolybdate and ferricyanide at cryogenic temperatures. In the presence of silicomolybdate or ferricyanide, two chlorophyll cation radicals were observed from P680+ (0.8 mT) and monomeric Chl (1.0 mT). Reduction of silicomolybdate was detected as a 2.7 mT signal at g = 1.942. A radical attributed to a tyrosine cation radical (D+/Z+) was also observed in a small percentage of centres.
Crystal structure of thermitase from Thermoactinomyces vulgaris at 2.2 Å resolution
Authors: Teplyakov Alexei V. , Kuranova Inna P. , Harutyunyan Emil H. , Frömmel Cornelius , Höhne Wolfgang E.
Published: July 2002

The crystal structure of thermitase from Thermoactinomyces vulgaris has been determined by X‐ray diffraction at 2.2 Å resolution. The structure was solved by a combination of single isomorphous replacement and molecular replacement methods. The structure was refined to a conventional R factor of 0.24 using restrained least square procedures CORELS and PROLSQ. The tertiary structure of thermitase is similar to that of subtilisin BPN′. The greatest differences between these structures are related to the insertions and deletions in the sequence.
Control of fructose 2,6‐bisphosphate levels in rat macrophages by glucose and phorbol ester
Authors: Bustos R. , Sobrino F.
Published: July 2002

The presence of fructose 2,6‐bisphosphate (Fru 2,6‐P2) in elicited peritoneal macrophages of rat was examined. These cells possess an active phosphofructokinase‐2 which is diminished by citrate and only slightly inhibited by glycerol 3‐phosphate. Phosphofructokinase‐1 submaximal activity was increased 26‐fold by the addition of 1 μM Fru 2,6‐P2. Incubation of cells without glucose decreased the amount of Fru 2,6‐P2 to zero, but further addition of 5 mM glucose increased the levels of the sugar ester 20‐fold. In addition, the presence of phorbol ester potentiated the synthesis of Fru 2,6‐P2. By contrast phenylisopropyladenosine or prostaglandin F2α inhibited the production of Fru 2,6‐P2.
Effect of denervation on the androgen‐induced expression of actin and CPK mRNAs in the levator ani muscle of the rat
Authors: Boissonneault Guylain , Tremblay Roland R.
Published: July 2002

In the adult male rat, the castration‐induced atrophy of the levator ani (LA) muscle was found to be associated with a decrease in the relative levels of both actin and creatine phosphokinase (CPK) mRNAs. The typical recovery of these two sequences following 5 days of testosterone propionate (TP) replacement therapy was not impaired by the bilateral denervation of the LA. This indicated that TP was the sole trophic factor regulating the plasticity of these two mRNAs and challenged the hypothesis that androgen action might be neuronally mediated. The observation that denervation led to a severe repression of both actin and CPK messages only in the absence of TP replacement therapy suggested that the nerve impulse could play an accessory role in the control of their expression.
Polyamine addition to preparation media induces chromatin condensation, irreversibly at low ionic strength
Authors: Colson P. , Houssier C.
Published: July 2002

Chromatin; Polyamine; Electric dichroism
Electrostatic coupling between membrane proteins
Authors: Brown Guy C.
Published: July 2002

Charges on membrane proteins are argued to produce very large electric fields within the membrane which may be felt by neighbouring membrane proteins. The activity of many membrane proteins may be sensitive to the electric field in the membrane; thus one membrane protein may affect the activity of another via the local electric field without any contact between the two. More specific electrostatic interactions are possible with binding between the two proteins. The possible roles of such interactions in bioenergetics, neurophysiology and signal transduction are discussed.
Induction of normal ultrastructure by CGRP treatment in dysgenic myotubes
Authors: Garcia Luis , Pinçon-Raymond Martine , Romey Georges , Changeux Jean-Pierre , Lazdunski Michel , Rieger François
Published: July 2002

The calcitonin gene‐related peptide (CGRP) restores an apparant normal ultrastructure in mdg/mdg muscle cells in vitro, including a normal triadic organization which is known to be essential for excitation‐contraction (E‐C) coupling. However, neither slow L‐type Ca2+ channel activity nor E‐C coupling, which are absent in mdg/mdg muscle, were re‐established. These observations suggest a potential role of CGRP (and also ofcAMP as the intracellular messenger) in the morphological development of the muscle fiber.
Nucleotide sequence determination of chicken glucagon precursor cDNA
Authors: Hasegawa Shin , Terazono Kimio , Nata Koji , Takada Tatsuyuki , Yamamoto Hiroshi , Okamoto Hiroshi
Published: July 2002

cDNA clones coding for glucagon were isolated from a chicken pancreas cDNA library, and the nucleotide and amino acid sequences were determined. The amino acid sequence of chicken glucagon was HSQGTFTSDYSKYLDSRRAQDFVQWLMST, which was contained in the 151‐amino acid long precursor, being preceded by a signal sequence and an amino‐terminal peptide (NH2‐peptide) and followed by an intervening peptide and a glucagon‐like peptide I (GLP‐I). Chicken preproglucagon, however, lacked GLP‐II and intervening peptide II which have been shown to be contained in mammalian glucagon precursors.
AS‐1 cyanophage infection inhibits the photosynthetic electron flow of photosystem II in Synechococcus sp. PCC 6301, a cyanobacterium
Authors: Teklemariam Thomas A. , Demeter Sándor , Deák Zsuzsa , Surányi Gyula , Borbély György
Published: July 2002

In Synechococcus sp. cells AS‐1 cyanophage infection gradually inhibits the photosystem II mediated photosynthetic electron flow whereas the activity of photosystem I is apparently unaffected by the cyanophage infection. Transient fluorescence induction and flash‐induced delayed luminescence decay studies revealed that the inhibition may occur at the level of the secondary acceptor, QB of photosystem II. In addition, the breakdown of D1‐protein is inhibited, comparable to DCMU‐induced protection of D1‐protein turnover, in AS‐1‐infected cells.
Widespread distribution of Gqα/Gllα detected immunologically by an antipeptide antiserum directed against the predicted C‐terminal decapeptide
Authors: Mitchell Fiona M. , Mullaney lan , Godfrey Philip P. , Arkinstall Steve J. , Wakelam Michael J.O. , Milligan Graeme
Published: July 2002

Antisera were raised to a synthetic peptide which represents the predicted C‐terminal decapeptide of the α subunit of the G‐proteins Gq and Gll. Competitive ELISA indicated that antiserum CQ2 displayed strong reactivity against this peptide. Antiserum CQ2 identified an apparently single polypeptide of 42 kDa which was expressed widely. The mobility of this polypeptide in SDS‐PAGE was not modified by pretreatment of cells with pertussis toxin, indicating that it was not a substrate for this toxin. Furthermore, the levels and mobility of this polypeptide were unaltered by treatment of cells with cholera toxin, defining that it was not related to Gsα.
Where is the glycolytic complex? A critical evaluation of present data from muscle tissue
Authors: Brooks S.P.J. , Storey K.B.
Published: July 2002

Assocaiations between glycolytic enzymes and subscellular structures have been interpreted as presenting a novel mechanism of glycolytic control; reversible enzymes binding to subcellular structural components is believed to regulate enzymes activity in vivo through the formation of a multi‐enzyme complex. However, three lines of evidence suggest that eyzyme binding to cellular structures is not involved in the control of glycolsis, (i) Calculations of the distribution of glycolytic enzymes under the physiological cellular conditions of higher ionic strenght and higher enzyme concentrations indicate that a large multi‐enzyme complex would not exist, (ii) In many eases, binding to subcellular structures is accompanied by changes in enzyme kinetic parameters brought about by allosteric modification, but these changes often inhibit enzyme activity, (iii) In the case where formation of binary enzyme/enzyme complexes activates enzymes, the overall increase in flux through the enzyme reaction is negible.
The δ subunit of the chloroplast ATPase is plastid‐encoded in the diatom Odontella sinensis
Authors: Pancic Peter G. , Strotmann Heinrich , Kowallik Klaus V.
Published: July 2002

A 5.2 kb PstI restriction fragment containing the atpA gene cluster of the plastic genome of the centric diatom Odontella sinensis was cloned. Sequencing revealed a reading frame of 561 bp separating the genes atpF and atpA, which is preceded by a putative ribosome binding site. The third nucleotide of the codon for the last amino acid of atpF is the first nucleotide of the initiation codon of the 561 bp reading frame. The amino acid sequence deduced from the nucleotide sequence of this gene (ntpD) is colinear with δ subunits of different F0F1‐ATPases and shows an overall sequence homology of up to 35% when compared with the sequences of cyanobacteria and Cyanophora paradoxa. The results are discussed in context with the evolution of chloroplasts of the chlorophyll‐a + b and ‐a + c lineages, respectively.
Relationship between surface hydrophilicity of a protein and its stability against denaturation by organic solvents
Authors: Khmelnitsky Yuri L. , Belova Alla B. , Levashov Andrey V. , Mozhaev Vadim V.
Published: July 2002

The stability of α‐chymotrypsin covalently modified with a strongly hydrophilic modifier, pyromellitic dianhydride, against solvent‐induced denaturation in water—organic solvent binary mixtures has been studied. It was found that the hydrophilization results in a strong stabilization of the enzyme against denaturation by organic solvents. The stabilizing effect is explained in terms of the enhanced ability of the hydrophilized enzyme to keep its hydration shell, which is indispensable for supporting the native protein conformation, from denaturing stripping by organic solvents
Fracture healing induces expression of the proto‐oncogene c‐fos in vivo Possible involvement of the Fos protein in osteoblastic differentiation
Authors: Ohta Shuichi , Yamamuro Takao , Lee Kaechoong , Okumura Hideo , Kasai Ryuichi , Hiraki Yuji , Ikeda Toshihiko , Iwasaki Rempei , Kikuchi Haruki , Konishi Junji , Shigeno Chohei
Published: July 2002

Here we report marked in vivo expression of the c‐fos gene in the external soft callus (ESC) and periosteal hard callus (PHC) at the fracture site of adult rat tibia. Northern‐blot analysis showed that the ESC expressed a high level of c‐fos mRNA from post‐fracture day 10 to day 28, the time when endochondral ossification progressed, and that the ossifying PHC also expressed c‐fos mRNA. This c‐fos expression was followed by sequential expression of the genes for alkaline phosphatase, osteopontin and osteocalcin, which are osteoblastic markers. Immunohistochemical analysis showed that the c‐Fos protein was predominantly located in osteoblasts in the ossifying calluses.
Differential expression of GABAA receptor α‐subunits in rat brain during development
Authors: McKernan R.M. , Cox P. , Gillard N.P. , Whiting P.
Published: July 2002

Unique cytoplasmic loop regions of the α1, α2, α3 and α5 subunits of the GABAA receptor have been expressed in E. coli and used to generate polyclonal antisera specific for these subunits. The antibodies identify proteins by SDS‐polyacrylamide gel electrophoresis and western blotting of molecular size 51 kDa, 53 kDa, 59 kDa and 55 kDa, respectively, which show differential patterns of expression during development. Whereas the α2 and α3 subunits are present at early stages, the expression of α1 and α5 subunits is low at birth and increases with age. This differential expression could be correlated with previous studies examining the developmental expression of BZ1 and BZ2 benzodiazepine binding sites.
Nucleotide sequence of a novel δ‐endotoxin gene cryIg of Bacillus thuringiensis ssp. galleriae
Authors: Smulevitch S.V. , Osterman A.L. , Shevelev A.B. , Kaluger S.V. , Karasin A.I. , Kadyrov R.M. , Zagnitko O.P. , Chestukhina G.G. , Stepanov V.M.
Published: July 2002

A gene cryIg coding for entomocidal protein δ‐endotoxin of Bacillus thuringiensis ssp. galleriae str. 11‐67 named CryIG has been cloned and sequenced (EMBL accession number X58120). The deduced amino acid sequence that contains 1156 amino acid residues shows only 28% of identical residues, when compared with other δ‐endotoxins of the CryI family. The extent of identity is substantially higher for some regions of the sequence (‘conserved blocks’), that presumably bear important structural or functional properties. This implies that CryIG δ‐endotoxin follows the same type of polypeptide chain folding as other Cryl proteins, whereas peculiarities of primary structure help to explain its unique specificity.
Cloning of a bovine voltage‐gated K+ channel gene utilising partial amino acid sequence of a dendrotoxin‐binding protein from brain cortex
Authors: Reid Paul F. , Pongs Olaf , Dolly J.Oliver
Published: July 2002

Several variants of fast‐activating, voltage‐dependant K+ channels exist in the nervous system where they control cell excitability and synaptic transmission, some of which are blocked selectively by α‐dendrotoxin. Cloning of a K+ channel from bovine genomic DNA was achieved using a primer based on the N‐terminal sequence of the larger subunit from the purified toxin acceptor, in conjunction with secondary primers, in the polymerase chain reaction. The resultant amino acid sequence is highly homologous to RCK 5 already cloned from rat brain, which yields a K+ current susceptible to α‐dendrotoxin, when expressed in oocytes. These findings establish conclusively that the extensively characterised α‐dendrotoxin acceptor is a K+ channel protein.
Stimulation of protein kinase C (PKC) activity in resting Swiss 3T3 cells by prostaglandin F2α
Authors: Goin Mercedes , de Asua Luis Jimenez
Published: July 2002

Prostaglandin F2α (PGF2α), a mitogen for resting Swiss 3T3 cells, rapidly stimulates phosphorylation of an 80 kDa protein (80 K). 1‐Oleoyl‐2‐acetylglycerol (OAG) and 12‐O‐tetradecanoyl phorbol‐13‐acetate (TPA) both protein kinase C (PKC) activators, also elicit 80 K phosphorylation. In contrast PGE1, PGE2 or PGF2β, which are non‐mitogenic in these cells, had tittle or no action on this event. However PGE1 and PGE2 potentiate the PGF2α proliferative effect but do not enhance its action on 80 K phosphorylation. These results suggest that PGF2α mitogenic induction involves PKC signalling pathway activation while its enhancement by PGE1 or PGE2 occurs through a different mechanism(s).
Isolation and some properties of a 34‐kDa‐membrane protein that may be responsible for ribosome binding in rat liver rough microsomes
Authors: Ichimura Tohru , Ohsumi Tomoya , Shindo Yukiko , Ohwada Tamotsu , Yagame Harutaka , Mornose Yasunori , Omata Saburo , Sugano Hiroshi
Published: July 2002

We have isolated, by hydroxyapatite chromatography with a non ionic detergent and a high salt concentration, a non‐glycosylated, membrane protein with a relative molecular weight of 34 kDa that had previously been found to be a major constituent of the membrane protein fraction showing ribosoine‐binding activity derived from rat liver rough microsomes (RM). The isolated 34 kDa protein (p34), when incorporated into a liposome model membrane, exhibited significant binding activity toward ribosomes, its binding properties being similar to those observed with intact R.M. immunochemical analyses using antibodies directed against p34 suggested that it is a membrane‐embedded RM surface protein, which is specifically localized in ribosome‐attached organelles and widely distributed among mammalian tissues. These results would constitute evidence that p34 is a likely candidate for an RM ribosome‐binding, protein.
Recognition of transition metal ions by peptides Identification of specific metal‐binding peptides in proteolytic digest maps by UV laser desorption time‐of‐flight mass spectrometry
Authors: Hutchens T.William , Nelson Randall W. , Yip Tai-Tung
Published: July 2002

Metal‐binding peptides in proteolytic digest maps have been identified by matrix‐assisted UV laser desorption time‐of‐flight mass spectrometry (LDTOF‐MS). The plasma and milk metal transport protein chosen to demonstrate this process, histidine‐rich glycoprotein (HRG), was purified and then digested with trypsin; the cleavage products were analyzed by LDTOF‐MS with dihydroxbenzoic acid as the matrix. The selective interaction of specific peptides with one or more Cu atoms was observed when Cu(II) ions were added to the digest mixture. At least one specific metal‐binding peptide was identified by computerized sequence analysis using the molecular mass data and available cDNA sequence. These results demonstrate the first direct observation by mass spectrometry of differential peptide—metal ion interactions in protein digest maps. The ability to evaluate peptide—metal ion interactions, including stoichiometry, with less than 1 pmol of sample improves significantly our ability to identify metal binding domains in metal‐binding proteins.
Autophagic degradation of peroxisomes in isolated rat hepatocytes
Authors: Luiken J.J.F.P. , van den Berg M. , Heikoop J.C. , Meijer A.J.
Published: July 2002

Degradation of the peroxisomal enzymes fatty acyl‐CoA oxidase and catalase was studied in hepatocytes isolated from rats treated with clofibrate and from control rats. Hepatocytes were incubated in the absence of amino acids in order to ensure maximal flux through the autophagic pathway and in the presence of cycloheximide to inhibit protein synthesis. (1) Degradation of the two peroxisomal enzymes in hepatocytes from clofibrate‐fed rats, but not in hepatocytes from control rats, was much faster than that of other intracellular enzymes. This increased degradation of the peroxisomal enzymes was almost completely prevented by 3‐methyladenine, an inhibitor of macroautophagic sequestration. (2) The increased degradation of the peroxisomal enzymes was also inhibited by a long‐chain (C16:0) and a very‐long‐chain (C26:0) fatty acid, but not by C12:0, a medium‐chain fatty acid, or by C8:0, a short‐chain fatty acid. These results provide direct evidence for the proposal that autophagic sequestration can be highly selective [(1987) Exp. Mol. Pathol. 46, 114–122]. It is concluded that preferential autophagy of peroxisomes is prevented when these organelles are supplied with their fatty acid substrates.
Thrombin‐induced human platelet aggregation is inhibited by protein‐tyrosine kinase inhibitors, ST638 and genistein
Authors: Asahi Momoyo , Yanagi Shigeru , Ohta Shinji , Inazu Tetsuya , Sakai Keiko , Takeuchi Furnito , Taniguchi Takanobu , Yamamura Hirohei
Published: July 2002

We have investigated the involvement of protein‐tyrosine kinases in thrombin‐induced aggregation of human platelets, using ST638 and genistein which are known inhibitors of protein‐tyrosine kinase. Preincubation of platelets with 50 μM of ST638 or 25 μg/ml of genistein completely blocked the platelet aggregation induced with 0.05 unit/ml of thrombin. The increase of protein‐tyrosine phosphorylation bands (135‐, 124‐, 76‐, 64‐, and 60‐kDa) induced with thrombin was also inhibited by these inhibitors in a dose‐dependent manner. These inhibitors also blocked the platelet aggregation and protein‐tyrosine phosphorylation induced with thrombin in aspirin‐treated platelets. Increase of the intracellular Ca2+ concentration induced by thrombin was also inhibited by higher concentrations of genistein. The results suggest that the protein‐tyrosine phosphorylation plays a certain role in platelet activation having some relation to the intracellular Ca2+ concentration.
cDNA sequence analysis of an antibiotic dodecapeptide from neutrophils
Authors: Storici Paola , Del Sal Giannino , Schneider Claudio , Zanetti Margherita
Published: July 2002

The full‐length cDNA of a neutrophil antibiotic dodecapeptide has been cloned by reverse transcription/PCR from bovine bone marrow RNA. This peptide was originally isolated from bovine neutrophils, and shown to exert a potent antimicrobial activity in vitro on both Escherichia coli and Staphylococcus aureus. The cDNA codes for a polypeptide of 155 amino acid residues with a predicted mass of 17,629 Da and a pl of 8.03. The deduced sequence comprises a putative signal peptide of 29 amino acids, a 114 residue pro‐region, and a carboxy‐terminal dodecapeptide corresponding to the mature antibiotic. The pro‐sequence displays extensive identity to corresponding regions of other structurally unrelated antibiotic peptides of bovine neutrophils recently cloned.
Phosphorylated cystatin α is a natural substrate of epidermal transglutaminase for formation of skin cornified envelope
Authors: Takahashi Masae , Tezuka Tadashi , Katunuma Nobuhiko
Published: July 2002

Both keratohyalin granules (KHG) and cornified envelopes were stained histochemically in an indirect immunofluorescent study by antiphosphorylated cystatin α antibody, indicating that phosphorylated cystatin α is a component of the cornified envelope proteins. When phosphorylated cystatin α (P‐cystatin α) was incubated with epidermal transglutaminase (TGase) and Ca2− ions, polymerized protein was produced by formation of ϵ‐(γ‐glutamyl)lysine cross‐linking peptide bonds between lysine residues of cystatin α and glutamine residues of suitable protein(s) in the enzyme preparation. However, phosphorylated and non‐phosphorylated cystatins were polymerized to similar extents by the TGase. Immunofluorescent and immunoelectron microscopic observations revealed that P‐cystatin α could be detected in vivo in the KHG and cornified envelopes. Treatment of sphingosine, a specific inhibitor of protein kinase C, markedly suppressed the incorporation of cystatin α into KHG. Thus phosphorylation of cystatin α by protein kinase C may play an important role in targeting cystatin α into KHG.
N‐Acetylaspartylglutamate acts as an agonist upon homomeric NMDA receptor (NMDAR1) expressed in Xenopus oocytes
Authors: Sekiguchi Masayuki , Wada Keiji , Wenthold Robert J.
Published: July 2002

The electrophysiological effects of N‐acetylaspartylglutamate (NAAG), an endogenous peptide restrictively distributed in the central nervous system, were studied using, Xenopus oocytes injected with RNAs transcribed from cloned glutamate receptor cDNAs. NAAG induced an inward current, dose dependently, in oocytes injected with RNA for an N‐methyl‐D‐aspartate receptor subunit (NMDAR1), In contrast, the oocytes injected with RNAs for AMPA‐selective glutamate receptors (GluR1, GluR3, GluR1+GluR2 and GluR2+GluR3) scarcely responded to NAAG, and the oocytes injected with RNA for kainate receptor (GluR6) did not respond to NAAG. The half‐maximal response (ED50) value of NAAG on expressed NMDAR1 was 185 μM, which shows that NAAG is about 115‐times less potent than L‐glutamate (Glu), the ED50 of which value was 1.6, μM. The maximal current amplitude induced by NAAG was about 70% of that by Glu. NAAG‐induced current in NMDAR1‐injected oocytes was potentiated by glycine, dose‐dependently antagonized by DL‐2‐amino‐5‐phosphonovaleric acid, and blocked by magnesium ions in a voltage‐dependent fashion. These results suggest that NAAG is one of the endogenous agonists selective for NMDAR1.
Homologous sucrose synthase genes in barley (Hordeum vulgare) are located in chromosomes 7H (syn. 1 and 2H Evidence for a gene translocation?
Authors: de la Hoz Pilar Sánchez , Vicente-Carbajosa Jesús , Mena Montaña , Carbonero Pilar
Published: July 2002

The chromosomal location of the two types of sucrose synthase genes, Ss1 and Ss2, has been investigated in barley by Southern blot analysis of wheat‐barley addition lines using non‐cross‐hybridizing‐specific probes corresponding to the C‐terminal regions of their respective CDNA clones (⋍250 bp). The Ss1 gene, whose cDNA of 2,667 bp has been entirely sequenced, is located in the β‐arm of chromosome 7H (syn. 1), while that corresponding to the homologous Ss2 is in the short arm of 2H, suggesting the existence of a translocation event between these two chromosomes in cultivated barley after an initial gene duplication and divergent evolution.
A novel specific binding site for anxiolytic homophthalazines in the rat brain
Authors: Salamon Cecilia , Horváth Edit J. , Fekete Márton I.K. , Arányi Péter
Published: July 2002

Radioligand binding studies were performed in order to elucidate the mechanism of action of anxiolytic‐neuroleptic homophthalazines. Rat striatal membrane preparations were found to bind 3H‐EGIS 6775 [3H‐GYKI‐52 322, 3H‐(I‐(4‐aminophenyl)‐4‐methyl‐7,8‐dimethoxy‐5H‐homophthalazine)] in a specific and displaceable manner. Several other brain regions tested were devoid of similar binding activity. Saturation analysis revealed that binding affinity was in the 10−5‐10−7 M range. Binding was enhanced by Mg2+ ions and, to a smaller extent by Ca2+ ions. The binding principle was sensitive to heat or trypsin treatment. This specific binding site appears, according to competition studies, different from the receptors whose presence in the rat striatum has been reported earlier.