bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Refined Quaternary Structure of Androctonus australis Hemocyanin
Authors: SIZARET Pierre‐Yves , FRANK Joachim , LAMY Josette , WEILL Jacques , LAMY Jean N. 
Published: July 2010

The quaternary structure of the (4 × 6)‐mer hemocyanin from the scorpion Androctonus australis previously published [Lamy, J., Bijlholt, M. M. C., Sizaret, P.‐Y., Lamy, J., and van Bruggen, E. F. J. (1981) Biochemistry, 20, 1849–1856] has been refined. The relative positions in the half molecule of subunits Aa 3 A and Aa 3B compared to those of Aa 3C and Aa 5B have been established by double labeling of the (2 × 6)‐mer with binary mixtures of subunit‐specific Fab fragments. The results show that subunits Aa 3B and Aa 5B are located in the same hexamer while Aa 3A and Aa 3C are in the other half of the (2 × 6)‐mer.The choice of the enantiomer was deduced from a careful examination of electron micrographs of the native molecule. Finally a position was assigned to each of the 24 subunits on the flip and flop faces as defined by Van Heel and Frank [Ultramicroscopy, 6, 187–194 (1981)].
Affinity Labeling of Glyceraldehyde‐3‐phosphate Dehydrogenase from Sturgeon and Bacillus stearothermophilus by 3‐Chloroacetylpyridine–adenine Dinucleotide
Authors: BRANLANT Guy , EILER Brigitte , WALLEN Leif , BIELLMANN Jean‐François 
Published: July 2010

The inactivation of glyceraldehyde‐3‐phosphate dehydrogenase from Bacillus stearothermophilus and sturgeon by 3‐chloroacetylpyridine–adenine dinucleotide, which is not active as a coenzyme, obeys pseudo‐first‐order kinetics. The mechanism of inactivation corresponds to an affinity label. Four moles of inactivator are incorporated per mole of tetramer for both enzymes. All the kinetic results strongly support the idea that neither enzyme exhibits negative cooperativity for the non‐covalent binding of 3‐chloroacetylpyridine–adenine dinucleotide.NAD+ strongly protects both glyceraldehyde‐3‐phosphate dehydrogenases from inactivation. In the presence of NAD+, the inactivation process seems also to exhibit pseudo‐first‐order kinetics. The fact that each kinetic experiment can be described by only one pseudo‐first‐order rate constant is unexpected.The results of thiol titration are in favor of the modification of the essential Cys‐149, although another thiol group per monomer, probably Cys‐153, becomes titratable on both native alkylated enzymes. This latter result suggests that the alkylation of the Cys‐149 by the 3‐chloroacetylpyridine–adenine dinucleotide should affect the tertiary structure of these enzymes.
Synthesis of Peptidoglycan in vivo in Methicillin‐Resistant Staphylococcus aureus
Authors: WYKE Anne W. , WARD J. Barrie , HAYES Michael V. 
Published: July 2010

The cell‐wall composition and degree of cross‐linking of peptidoglycan in a strain of Staphylococcus aureus (strain MR‐1) which is highly resistant to methicillin were similar to those of other strains of S. aureus. When the organism was grown in the presence of very low concentrations of methicillin (equivalent to 3 · 10−4× minimum growth‐inhibitory concentration [MGIC] there was a large decrease in the degree of cross‐linking of the peptidoglycan. Increasing concentrations of methicillin (up to 1.25 · 10−2× MGIC) caused a further decrease in cross‐linkage but thereafter a minimum value was reached. This remained unchanged even after growth of the organisms in much higher concentrations of the antibiotic up to 0.3 × minimum growth‐inhibitory concentration. S. aureus MR‐1 was able to grow normally for many generations under these conditions and reduction in cross‐linkage of peptidoglycan was the only change detected in wall chemistry. Growth in the presence of methicillin (up to 0.3 × MGIC) (or other β‐lactam antibiotics) did not lead to an imbalance in the biosynthesis of peptidoglycan since no soluble polymers were secreted into the growth medium and nucleotide‐linked precursors did not accumulate intracellularly.High concentrations of β‐lactam antibiotics (5 × MGIC) were bacteriostatic not bactericidal and this may be related to an apparent deficiency in the endogenous autolytic enzymes of strain MR‐1.Studies of the penicillin‐binding proteins after growth in the presence of methicillin suggest that one of these proteins remains resistant to very high concentrations of the antibiotic. We propose that this protein acts as the primary transpeptidase responsible for the incorporation of newly synthesised peptidoglycan into the growing wall.
Purification and Properties of Protein Methylase II from Wheat Germ
Authors: TRIVEDI Leena , GUPTA Arun , KI PAIK Woon , KIM Sangduk 
Published: July 2010

Protein methylase II (S‐adenosylmethionine:protein‐carboxyl O‐methyltransferase, EC 2.1.1.24) was purified from wheat germ approximately 1200‐fold with a yield of 4.6% by employing gel filtration. The enzyme, using S‐adenosyl‐l‐methionine, methyl‐esterifies the free carboxyl group of protein. Since the enzymatic product was unstable and hydrolyzed non‐enzymatically to yield methanol, methanol was identified from the hydrolysate by the formation of the methyl ester of 3, 5‐dinitrobenzoate. The pH optimum for the wheat germ enzyme was 7.0 in contrast to the 6.0 for the methylase II of calf brain. The wheat germ enzyme had a molecular weight of 41000 compared to 25000 for the corresponding rat erythrocyte enzyme [S. Kim (1975) Arch. Biochem. Biophys. 161, 652–657]. The enzyme also differed with the mammalian enzyme in protein substrate preference: the mammalian enzyme showed equal preference to histone and immunoglobulin G while the wheat germ enzyme transferred a methyl group 4.5 times more to histone than to immunoglobulin G. The Km values for histone and S‐adenosyl‐l‐methionine were 0.2 mM and 5 μM. S‐Adenosyl‐l‐homocysteine and its analogues, sinefungin and A9145C, were competitive inhibitors with Ki values 1.5 μM, 0.4 μM and 0.1 μM, respectively.To investigate the identity of endogenous substrate(s) for protein methylase II, the crude wheat germ extract was incubated with S‐adenosyl‐l‐[methyl‐3H]methionine and the methylated proteins were analyzed by acid/urea and sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Among other methyl acceptors in the wheat germ, histone polypeptides were the major endogenous substrates.
Characterization of the Region on Protein L7/L12 Involved in Binding to Ribosomal Particles
Authors: SCHOP Enno N. , MAASSEN J. Antonie 
Published: July 2010

Tryptic digestion of reductively methylated protein L7/L12 yields a large tryptic fragment, which comprises amino acids 1–59. At the most, two molecules of this fragment can bind to a 50‐S ribosomal particle, deprived of protein L7/L12. Besides, binding of each single 1–59 fragment competes with binding of one dimeric L7/L12 molecule. Molecular weight studies on the fragment reveal a monomeric structure. Digestion of the 1–59 fragment with carboxypeptidase Y leads to the formation of a 1–55 fragment. The binding characteristics of the latter fragment are similar to those of the 1–59 fragment.The results suggest that a monomeric stretch of L7/L12, comprising the first 55 amino acids, is sufficient for attaching L7/L12 to the ribosome.
Binding and Exchange of Nucleotides on the Chloroplast Coupling Factor CF1
Authors: GIRAULT Guy , GALMICHE Jean‐Michel , LEMAIRE Claire , STULZAFT Oscar 
Published: July 2010

On the soluble part of the coupling factor (CF1), extracted from spinach chloroplasts, three nucleotide‐binding sites are identified. Three ADP are bound per CF1 when the enzyme is incubated with ADP either with or without Mg2+. Two ADP and one ATP are bound per CF1 when the enzyme is incubated with a limiting concentration of ATP, in the presence of Mg2+. At high ATP concentration, in the presence of Mg2+, one free ATP exchanges with one bound ADP and two ATP and one ADP remain bound per CF1. When Mg2+ is omitted from the incubation medium of ATP and CF1, only two ADP and around 0.5 ATP are bound per CF1.The three nucleotide binding sites of CF1 fall into two different and independent categories according to the ability of the bound nucleotides to be exchanged with free nucleotides. On one site the bound ADP is difficult to exchange. On the other two sites, the bound nucleotides, ADP or ATP, are readily exchangable.We propose that the two exchangeable sites form the catalytic part of the enzyme where ATP is hydrolyzed. When ATP concentration is high enough, in the presence of Mg2+, one ATP displaces one bound ADP and allows the ATP hydrolysis to proceed. We propose too that the site where ADP is difficult to exchange may represent the ‘tight’ ADP‐binding site, different from the catalytic ones, which becomes exchangeable on the CF1in vivo when the thylakoid membranes are energized by light, as stressed by Bickel‐Sandkötter and Strotman [(1976) FEBS Lett. 65, 102–106].
Dissociation of Apolipoprotein AI from Apoprotein‐Lipid Complexes and from High‐Density Lipoproteins
Authors: ROSSENEU Maryvonne , VAN TORNOUT Philippe , LIEVENS Marie‐José , SCHMITZ Gerd , ASSMANN Gerd 
Published: July 2010

The dissociation of the apoprotein AI (apoAI) from the apoAI‐dimyristoylglycerophosphocholine complex and from human high‐density lipoproteins (HDL), was induced by incubation with guanidinium hydrochloride at concentrations between 0 M and 7 M.The kinetics and extent of denaturation were followed by monitoring both the fluidity of the lipid phase by fluorescence polarization measurements and the protein conformation by measuring the tryptophanyl fluorescence emission.The association with lipids protects apoAI against denaturation both in HDL and in the apoAI‐phospholipid complex. The results of the kinetic and end‐point measurements suggest that the denaturing effect of guanidine hydrochloride on the apoAI‐lipid complex and on HDL is a two‐step process. It involves the dissociation of the apoAI‐phospholipid bond, as evidenced by fluidity measurements: this effect is maximal between 3 M and 4 M guanidine hydrochloride. The conformational change of the apoAI protein into a randomly coiled structure with the tryptophanyl residues exposed to the solvent is maximal between 4 M and 6 M guanidine hydrochloride.HDL and the apoAI‐phospholipid complex have a closely similar behaviour towards denaturation by guanidine hydrochloride indicating that the phospholipid‐apoAI association in HDL is primarly responsible for the stability of the lipoprotein molecule.
Isolation and Characterization of Nucleic‐Acid‐Like Polymers Containing Glucose from Ehrlich Ascites Tumor Cells
Authors: KAGAWA Haruo , KAGAWA Kazuko 
Published: July 2010

Novel nucleic‐acid‐like polymers containing glucose, glucose ‘nucleic acid’, were isolated from cytoplasmic particles of Ehrlich ascites tumor cells. It is assumed that the basic structure of the polymers is similar to those of known nucleic acids except that their sugar constituents are glucose derivatives instead of ribose or deoxyribose.
When the glucose ‘nucleic acid’ was incubated with venom phosphodiesterase, four kinds of glucose ‘nucleotides’ containing bases of cytosine, adenine, guanine and thymine were obtained.
When the polymers were incubated with both venom phosphodiesterase and alkaline phosphatase, inorganic phosphates of glucose ‘nucleotides’ were removed and each nucleotide was converted to a glucose ‘nucleoside’.
Interaction of β1‐Anticollagenase from Human Plasma with Collagenases from Various Tissues and Competition with α2‐Macroglobulin
Authors: MACARTNEY Henry W. , TSCHESCHE Harald 
Published: July 2010

β1‐Anticollagenase from human plasma forms an inactive enzyme‐inhibitor complex with active human polymorphonuclear leukocyte collagenase [Macartney, H. W. and Tschesche, H. (1983) Eur. J. Biochem. 130, 85–92]. The inhibitor was shown to contain a reactive sulfhydryl group necessary for inhibition of the collagenase. Inhibition of the enzyme by β1‐anticollagenase was shown to take place via a thiol/disulfide interchange reaction similar to the mechanism reported for the reaction between polymorphonuclear leukocyte collagenase and the polymorphonuclear collagenase inhibitor [Macartney, H. W. and Tschesche, H. (1980) FEBS Lett. 119, 327–332].The observations made in this paper have shown that the collagenases obtained from other human tissues, such as rheumatoid synovial fluid, embryonic skin fibroblasts, diabetic skin fibroblasts and normal skin fibroblasts, all react with β1‐anticollagenase via a thiol/disulfide interchange mechanism, and are inhibited in a 1:1 stoichiometric reaction.Reaction of the inhibitor with the collagenases can be blocked by alkylation of the inhibitor's free sulfhydryl group with iodoacetamide, or by reaction of the inhibitor with disulfide‐containing compounds such as cystine, oxidised glutathione, insulin, relaxin or trypsinogen.The β1‐anticollagenase–collagenase complexes (latent enzyme) can all be reactivated with disulfide‐containing compounds, such as those mentioned above. An activation process has been reported for human latent polymorphonuclear leukocyte collagenase via a thiol/disulfide interchange as catalysed by the glutathione cycle in a peroxidase‐coupled reaction to glucose metabolism [Tschesche, H. and Macartney, H. W. (1981) Eur. J. Biochem. 120, 183–190]. The same physiological activation process is capable of reactivating β1‐anticollagenase–collagenase complexes in a reversible manner.It was further shown in competition experiments with β1‐anticollagenase (and with human leukocyte collagenase inhibitor) and α2‐macroglobulin that vertebrate collagenases were preferentially inhibited by the low‐molecular‐weight inhibitors. It could also be shown that there was no transfer of the enzyme to α2‐macroglobulin from either β1‐anticollagenase–collagenase, or leukocyte inhibitor–collagenase complexes indicating a true inhibitory function for the β1‐anticollagenase and the leukocyte collagenase inhibitor.
Elicitor Induction of mRNA Activity
Authors: LAWTON Michael A. , DIXON Richard A. , HAHLBROCK Klaus , LAMB Chris J. 
Published: July 2010

Changes in the activity levels of mRNAs encoding phenylalanine ammonia‐lyase and chalcone synthase, two characteristic enzymes of phenylpropanoid biosynthesis, in elicitor‐treated cells of dwarf French bean (Phaseolus vulgaris L.) have been investigated by immunoprecipitation of [35S]methionine‐labelled enzyme subunits synthesised in vitro in an mRNA‐dependent rabbit reticulocyte lysate translation system.Elicitor heat‐released from cell walls of Colletotrichum lindemuthianum, the causal agent of anthracnose disease of bean, causes marked rapid increases in the polysomal activities of the mRNAs encoding the two enzymes concomitant with the phase of rapid increase in enzyme activity at the onset of phaseollin accumulation during the phytoalexin defence response.Increased polysomal mRNA activities encoding the two enzymes can be observed 30 min after elicitor treatment. The patterns of induction of the mRNA activities are broadly similar with respect to time and elicitor concentration although small but distinct differences between the enzymes were observed in the elicitor concentration giving maximum induction. There is a close correlation between the induction of polysomal mRNA activity and the induction of enzyme synthesis in vivo by elicitor treatment with respect to both the kinetics of induction and the dependence on elicitor concentration. The data indicate that elicitor stimulation of phenylalanine ammonia‐lyase and chalcone synthase synthesis in vivo is largely a result of increased polysomal activity of the mRNAs encoding these enzymes. Similar patterns of induction of polysomal mRNA activity are observed with elicitor preparations from a variety of sources.The marked increases in polysomal mRNA activities encoding phenylalanine ammonia‐lyase and chalcone synthase are increases as a proportion of total cellular mRNA activity, indicating that elicitor does not increase these polysomal mRNA activities by stimulation of selective recruitment from the total pool of cellular mRNA.
Translational Stability of Plant Viral RNAs Microinjected into Living Cells
Authors: HUEZ Georges , CLEUTER Yvette , BRUCK Claudine , VAN VLOTEN‐DOTING Lous , GOLDBACH Rob , VERDUIN Benedictus 
Published: July 2010

Three different alternative structural features have been shown to be present at the 3′ terminus of plant viral RNAs: (a) a poly(A) track, (b) a tRNA‐like structure, (c) no special structural or sequence characteristic. We have compared the translational stability after injection into frog oocytes of a representative of each type: (a) the small genomic RNA (M‐RNA) of cowpea mosaic virus (CPMV), (b) the subgenomic mRNA for coat protein (RNA 4) of brome mosaic virus (BMV), (c) the subgenomic mRNA for coat protein (RNA 4) of alfalfa mosaic virus (AIMV).It has been shown that CPMV M‐RNA exhibits the highest translational stability. However, the stability of AIMV RNA 4 is remarkably high and moreover significantly higher than that of BMV RNA 4.We demonstrate that, for all three viral RNA species considered, the presence of a poly(A) segment at the 3′ end of the molecules improves the translational stability. From a comparative investigation in which AIMV RNA 4 was also injected into HeLa cells, it is concluded that the stability of a given non‐adenylylated mRNA depends on the nature of the cytoplastic environment.
Structure of Six 3‐Deoxy‐d‐Glycero‐d‐Galacto‐Nonulosonic Acid(Kdn)‐Containing Oligosaccharide‐Alditols Released from Oviduct Secretions of Ambystoma Maculatum
Authors: Fontaine Marie‐Dominique , Wieruszeski Jean‐Michel , Plancke Yves , Delplace Florence , Strecker Gerard 
Published: July 2010

TheO‐linked acidic oligosaccharides of the jelly coat surrounding the eggs of Ambystoma maculatum were analyzed by NMR spectroscopy. The structures of the major oligosaccharides were established as follows where Kdn represents 3‐deoxy‐d‐glycero‐d‐galacto‐nonulosonic acid and GalNAc‐ol is N‐acetylgalactosaminitol:
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As shown for five other amphibian species, the structures of these carbohydrate chains appear to be species specific and can afford a basis for molecular taxonomy. These new sequences also reflect the occurrence of specific fucosyltransferase activities that are characteristic of Ambystoma maculatum.
Octanoate Affects 2,4‐Dinitrophenol Uncoupling in Intact Isolated Rat Hepatocytes
Authors: Sibille Brigitte , Keriel Christiane , Fontaine Eric , Catelloni Françoise , Rigoulet Michel , Leverve Xavier M. 
Published: July 2010

When intact isolated rat hepatocytes, either incubated or perifused, were uncoupled by 2,4‐dinitrophenol, we found that the effect on glucose and lactate+pyruvate fluxes, cytosolic and mitochondrial redox states and ATP/ADP ratios were dependent on the nature of the exogenous substrate added. 2,4‐Dinitro‐phenol addition (0.25 mmol/1) to cells perifused with dihydroxyacetone (10 mmol/1) resulted in a modest and transient activation of oxygen uptake accompanied by a surprising rise in lactate/pyruvate ratio indicating an increase in the cytosolic NADH/NAD+ ratio. In addition, such uncoupling, fully abolished glucose production, enhanced lactate+pyruvate flux, and strongly decreased cytosolic and mitochondrial ATP/ADP ratios. In these steady‐state conditions, further addition of Octanoate (0.4 mmol/1) induced a large and sustained enhancement of respiration with a concomitant decrease in the lactate/pyruvate ratio, whereas glucose flux was restored to some extent and cytosolic and mitochondrial ATP/ADP ratios increased. Inhibition of the malate‐aspartate shuttle by the transaminase inhibitor aminooxyacetate (0.3 mmol/1) did not modify the effect of 2,4‐dinitrophenol with dihydroxyacetone alone whereas it decreased the maximal stimulation of oxygen uptake after octanoate addition.In view of these results we propose the following conclusions.The uncoupling of intact cells by 2,4‐dinitrophenol inhibits the translocation of reducing equivalents into the mitochondrial matrix probably by impairing the malate‐aspartate shuttle. This explains the increase in the cytosolic NADH/NAD4 ratio and the transient activation of respiration with dihydroxyacetone.Fatty acid addition to cells uncoupled with 2,4‐dinitrophenol appears to restore a mitochondrial membrane potential, probably by providing the respiratory chain with reduced cofactors directly in the matrix, thus allowing the transfer of reducing equivalents across the mitochondrial membrane.The restoration, to some extent, of a protonmotive force to uncoupled cells by fatty acid addition is also supported by an increase in ATP synthesis as evidenced by a glucose synthesis with dihydroxyacetone as gluconeogenic substrate.
Structure of the N‐Linked Oligosaccharides from Tridacnin, a Lectin Found in the Haemolymph of the Giant Clam Hippopus Hippopus
Authors: Puanglarp Narongsak , Oxley David , Currie Graeme J. , Bacic Antony , Craik David J. , Yellowlees David 
Published: July 2010

Tridacnin, a glycoprotein lectin, was isolated from the symbiotic marine clam Hippopus hippopus and the structure of its major N‐glycan chains determined. Tridacnin contains only N‐linked glycans which were quantitatively cleaved by peptide‐N4‐(N‐acetyl‐β‐glucosaminyl)asparagine amidase F. Following purification by anion‐exchange HPLC, the structures of the oligosaccharides were established using a combination of electrospray ionisation mass spectrometry, 1H‐NMR spectroscopy and linkage analysis. The N‐glycans are primarily of the oligomannose type but, in addition, some contain a novel 6‐O‐Me group on the terminal mannose residue of the chain. The N‐glycan chains had the following structures.
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