bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interaction of phalloidin with chemically modified actin
Authors: MIKI Masao , BARDEN Julian A. , dos REMEDIOS Cristobal G. , PHILLIPS Leonidas , HAMBLY Brett D. 
Published: March 2005

Modification of Tyr‐69 with tetranitromethane impairs the polymerizability of actin in accordance with the previous report [Lehrer, S. S. and Elzinga, M. (1972) Fed. Proc. 31, 502]. Phalloidin induces this chemically modified actin to form the same characteristic helical thread‐like structure as normal F‐actin. The filaments bind myosin heads and activate the myosin ATPase activity as effectively as normal F‐actin. When a dansyl group is introduced at the same point [Chantler, P. D. and Gratzer, W. B. (1975) Eur. J. Biochem. 60, 67–72], phalloidin still induces the polymerization. The filaments bind myosin heads and activate the myosin ATPase activity. These results indicate that Tyr‐69 is not directly involved in either an actin‐actin binding site or the myosin binding site on actin. Moreover, the results suggest that phalloidin binds to actin monomer in the presence of salt and its binding induces a conformational change in actin which is essential for polymerization, or that actin monomer fluctuates between in unpolymerizable and polymerizable form while phalloidin binds to actin only in the polymerizable form and its binding locks the conformation which causes the irreversible polymerization of actin.Modification of Tyr‐53 with 5‐diazonium‐(1H)tetrazole blocks actin polymerization [Bender, N., Fasold, H., Kenmoku, A., Middelhoff, G. and Volk, K. E. (1976) Eur. J. Biochem. 64, 215–218]. Phalloidin is unable to induce the polymerization of this modified actin nor does it bind to it. Phalloidin does not induce the polymerization of the trypsin‐digested actin core. These results indicate that the site at which phalloidin binds is involved in polymerization and the probable conformational change involved in polymerization may be modulated through this site.
Purification and characterization of a β‐glucosidase from Trichoderma reesei
Authors: CHIRICO William J. , BROWN Ross D. 
Published: March 2005

A β‐glucosidase has been purified from culture filtrates of the fungus Trichoderma reesei QM9414 grown on microcrystalline cellulose. The β‐glucosidase was purified using two successive DEAE‐Sephadex anion‐exchange chromatography steps, followed by SP‐Sephadex cation‐exchange chromatography and concanavalin‐A–agarose chromatography. Evidence for homogeneity is provided by polyacrylamide disc gel electrophoretic patterns, which show a single protein band.Sedimentation equilibrium analysis yielded a molecular mass of 74.6 ± 2.4 kDa. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis yielded a single protein band with a molecular mass of 81.6 kDa. Thus, the enzyme appears to be a single, monomeric polypeptide. The β‐glucosidase is isoelectric at pH 8.5. The enzyme is rich in basic amino acids and contains few half‐cystine and methionine residues. The purified β‐glucosidase contains less than 1% by weight of neutral carbohydrate.The β‐glucosidase catalyzes the hydrolysis of cellobiose, p‐nitrophenyl β‐d‐glucopyranoside and 4‐methyl‐umbelliferyl β‐d‐glucopyranoside; the values of V/Km for each substrate were determined to be 2.3 × 104, 6.9 × 105 and 2.9 × 106 M−1 s−1 respectively. The enzyme is optimally active from pH 4.5 to 5.0 and is labile at higher hydrogen ion concentrations. The β‐glucosidase has an unusually high affinity for d‐glucose (Ki= 700 μM). Comparison of inhibition constants for cello‐oligosaccharides suggests that the substrate‐binding region of the β‐glucosidase comprises multiple subsites.
Conformational transitions in the myosin head induced by temperature, nucleotide and actin
Authors: RȨDOWICZ Maria J. , SZILÁGYI Laszlo , STRZELECKA‐GOLASZEWSKA Hanna 
Published: March 2005

Tryptic digestion patterns reveal a close similarity of the substructure of frog subfragment‐1 (S1) to that established for rabbit S1. The 97‐kDa heavy chain of chymotryptic S1 of frog myosin is preferentially cleaved into three fragments with apparent molecular masses of 29 kDa, 49 kDa and 20 kDa. These fragments correspond to the 27‐kDa, 50‐kDa and 20‐kDa fragments of rabbit S1, respectively; this is indicated by the sequence of their appearance during digestion, by the suppression by actin of the generation of the 49‐kDa and 20‐kDa peptides, and by a nucleotide‐promoted cleavage of the 29‐kDa peptide to a 24‐kDa fragment and the 49‐kDa peptide to a 44‐kDa fragment, analogous to the nucleotide‐promoted cleavage of the 27‐kDa and 50‐kDa fragments of rabbit S1 to the 22‐kDa and 45‐kDa peptides.The same changes in the digestion patterns as those produced by the presence of nucleotide (ATP or its β, γ‐imido analog AdoPP[NH]P) at 25 °C were observed when the digestion was carried out at 0 °C in the absence of nucleotide. The low‐temperature‐induced changes were particularly well seen in the preparations from frog myosin. The presence of ATP or AdoPP[NH]P at 0 °C enhanced, whereas the complex formation with actin prevented, the low‐temperature‐induced changes. The results are consistent with there being two fundamental conformational states of the myosin head in an equilibrium that is dependent on the temperature, the nucleotide bound at the active site, and the presence or absence of actin.
Conformational analysis and the fine structure of cross peaks in phase‐sensitive homonuclear two‐dimensional correlated NMR spectra of oligosaccharides
Authors: BERMAN Elisha 
Published: March 2005

Useful structural and conformational information was obtained from a detailed analysis of the fine structure of cross peaks that appears in the phase‐sensitive homonuclear correlated two‐dimensional spectra of complex large glycopeptides. The small chemical shift range observed for the oligosaccharide part results in a variety of cross‐peak patterns. A catalogue of cross‐peak fine structures and patterns expected for common carbohydrates are presented which can help in making some, all‐important and crucial, proton resonance assignments.Analysis of the vicinal coupling constants extracted from the cross peaks corresponding to the hydroxymethyl protons of the inner core carbohydrates of glycopeptides derived from calf fetuin, has yielded information regarding the time‐averaged solution conformation of this triantennary structure. It was shown that in solution the Man(α1–6) arm of the core pentasaccharide unit, which carries a single antenna, adopts for an appreciable part of the time a conformation which brings it close to the arm that is attached to the peptide part. A similar conformation for the Man(α1–6) arm was previously observed for the biantennary oligosaccharide chain. Therefore, we concluded that the presence of an additional antenna on the Man(α1–3) arm of the core unit in the triantennary structure does not alter the basic biantennary conformation.
Possible involvement of eicosanoids in the zymosan and arachidonic‐acid‐induced oxygen uptake, glycogenolysis and Ca2+ mobilization in the perfused rat liver
Authors: DIETER Peter , ALTIN Joseph G. , DECKER Karl , BYGRAVE Fyfe L. 
Published: March 2005

Exposure of perfused rat livers to zymosan, arachidonic acid and phenylephrine, but not to latex particles, induces pronounced oxygen uptake, glycogenolysis and Ca2+ mobilization. The oxygen uptake induced by arachidonic acid and by zymosan remains elevated even after the agents have been removed. NaN3 was found to be much more effective in inhibiting the oxygen uptake induced by phenylephrine than that induced by zymosan or arachidonic acid.Glucose release induced by zymosan and by arachidonic acid reaches a maximum after about 2 min and then declines very rapidly even while the agents are still being infused. In contrast, glucose release induced by phenylephrine remains elevated for the duration of the infusion.Ca2+ fluxes induced by arachidonic acid are similar to those induced by phenylephrine in that efflux occurs when the agent is administered and influx occurs only when the agent is removed. This contrasts to the Ca2+ flux changes induced by zymosan where both Ca2+ efflux and Ca2+ influx occur even while zymosan is still being infused.Glucose release induced by zymosan is inhibited by bromophenacylbromide and nordihydroguaiaretic acid, but not by indomethacin. Indomethacin, however inhibits the arachidonic‐acid‐induced glucose release which is also inhibited by nordihydroguaiaretic acid but not by bromophenacylbromide. Indomethacin inhibits also the arachidonic‐acid‐induced Ca2+ flux changes whereas the zymosan‐ and the phenylephrine‐induced Ca2+ flux changes are not inhibited by the cyclooxygenase inhibitor.The data presented in this paper suggest that in the perfused rat liver the zymosan‐induced glycogenolysis, as well as the Ca2+ flux changes and glycogenolysis induced by arachidonic acid, are mediated by eicosanoids.
Nickel‐[iron‐sulfur]‐selenium‐containing hydrogenases from Desulfovibrio baculatus (DSM 1743)
Authors: TEIXEIRA Miguel , FAUQUE Guy , MOURA Isabel , LESPINAT Paul A. , BERLIER Yves , PRICKRIL Ben , PECK Harry D. , XAVIER António V. , Le GALL Jean , MOURA José J. G. 
Published: March 2005

The hydrogenase from Desulfovibrio baculatus (DSM 1743) was purified from each of three different fractions: soluble periplasmic (wash), soluble cytoplasmic (cell disruption) and membrane‐bound (detergent solubilization). Plasma‐emission metal analysis detected in all three fractions the presence of iron plus nickel and selenium in equimolecular amounts. These hydrogenases were shown to be composed of two non‐identical subunits and were distinct with respect to their spectroscopic properties. The EPR spectra of the native (as isolated) enzymes showed very weak isotropic signals centered around g∼ 2.0 when observed at low temperature (below 20 K). The periplasmic and membrane‐bound enzymes also presented additional EPR signals, observable up to 77 K, with g greater than 2.0 and assigned to nickel(III). The periplasmic hydrogenase exhibited EPR features at 2.20, 2.06 and 2.0. The signals observed in the membrane‐bound preparations could be decomposed into two sets with g at 2.34, 2.16 and ∼ 2.0 (component I) and at 2.33, 2.24, and ∼ 2.0 (component II). In the reduced state, after exposure to an H2 atmosphere, all the hydrogenase fractions gave identical EPR spectra.EPR studies, performed at different temperatures and microwave powers, and in samples partially and fully reduced (under hydrogen or dithionite), allowed the identification of two different iron‐sulfur centers: center I (2.03, 1.89 and 1.86) detectable below 10 K, and center II (2.06, 1.95 and 1.88) which was easily saturated at low temperatures. Additional EPR signals due to transient nickel species were detected with g greater than 2.0, and a rhombic EPR signal at 77 K developed at g 2.20, 2.16 and 2.0. This EPR signal is reminiscent of the Ni‐signal C (g at 2.19, 2.14 and 2.02) observed in intermediate redox states of the well characterized Desulfovibrio gigas hydrogenase (Teixeira et al. (1985) J. Biol. Chem. 260, 8942]. During the course of a redox titration at pH 7.6 using H2 gas as reductant, this signal attained a maximal intensity around ‐320 mV. Low‐temperature studies of samples at redox states where this rhombic signal develops (10 K or lower) revealed the presence of a fast‐relaxing complex EPR signal with g at 2.25, 2.22, 2.15, 2.12, 2.10 and broad components at higher field. The soluble hydrogenase fractions did not show a time‐dependent activation but the membrane‐bound form required such a step in order to express full activity. This indicates that the redox state of the isolated enzyme is important for the full expression of enzymatic activity. The catalytic properties were also followed by the proton‐deuterium exchange reaction. The isolated hydrogenases produced H2/HD ratios higher than those observed for non‐selenium‐containing hydrogenases.
Structure of the major triglycosyl phenol‐phthiocerol of Mycobacterium tuberculosis (strain Canetti)
Authors: DAFFÉ Mamadou , LACAVE Charlotte , LANÉELLE Marie‐Antoinette , LANÉELLE Gilbert 
Published: March 2005

Phenol‐phthiocerol glycolipids have been found previously in Mycobacterium leprae, M. kansasii, M. bovis and M. marinum, but not in M. tuberculosis. A search for such glycolipids in this latter species showed that the Canetti strains of M. tuberculosis synthesize a major triglycosyl phenol‐phthiocerol, accompanied by minor amounts of other glycolipids with a similar aglycone moiety.The triglycoside moiety has the following structure: 2,3,4‐tri‐O‐methyl L‐fucopyranosyl(α1→3)L‐rhamno‐pyranosyl(α1→3)2‐O‐methyl L‐rhamnopyranosyl(α1 –.The aglycone moiety consists in phenol‐phthiocerol (two homologs). Its two secondary alcohol functions are esterified by mycocerosic acids (homologs with 26–32 carbon atoms and with 2–4 methyl branches). The proposed structure differs on several points from the M. leprae glycolipids, but presents some analogy with the major glycolipid of M. kansasii.A minor monoglycosyl phenol‐phthiocerol was also studied. Its overall structure is very similar to that of M. bovis, with 2‐O‐methyl rhamnose as sugar moiety.
A novel archaebacterial NAD+‐dependent alcohol dehydrogenase
Authors: RELLA Rocco , RAIA Carlo A. , PENSA Marcella , PISANI Francesca M. , GAMBACORTA Agata , DE ROSA Mario , ROSSI Mosè 
Published: March 2005

An NAD+‐dependent alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) was detected in cellular extracts of the extreme thermophilic archaebacterium Sulfolobus solfataricus. The enzyme was purified to homogeneity and shown to be a dimer with a native molecular mass of 71 kDa by sucrose gradient centrifugation and SDS electrophoresis.The enzyme has a broad substrate specificity that includes linear and branched primary alcohols, linear and cyclic secondary alcohols, linear and cyclic ketones and anisaldehyde.The enzyme has an extraordinary thermophilicity and a remarkable thermostability, and appears to have some properties and a structure different from those previously described for thermophilic alcohol dehydrogenases.
Three different proteins exhibiting NAD‐dependent acetaldehyde dehydrogenase activity from Alcaligenes eutrophus
Authors: JENDROSSEK Dieter , STEINBÜCHEL Alexander , SCHLEGEL Hans G. 
Published: March 2005

The existence of three different proteins exhibiting NAD‐dependent acetaldehyde dehydrogenase activity was confirmed in Alicaligenes eutrophus. The fermentative alcohol dehydrogenase, which also exhibits acetaldehyde dehydrogenase activity, is one of these proteins. The other two proteins were purified from A. eutrophus N9A mutant AS4 grown on ethanol applying chromatography on DEAE‐Sephacel and triazine‐dye affinity media. Acetaldehyde dehydrogenase II, which amounts to about 14% of the total soluble protein in cells grown on ethanol, was purified to homogeneity. The relative molecular masses of the native enzyme and of the subunits were 195 000 or 56 000, respectively. This enzyme exhibits a high affinity for acetaldehyde (Km= 4 μM). Acetaldehyde dehydrogenase I amounts only to less than 1% of the total soluble protein. The relative molecular masses of the native enzyme and of the subunits were 185 000 and 52 000, respectively. This enzyme exhibits a low affinity for acetaldehyde (Km= 2.6 mM). Antibodies raised against acetaldehyde dehydrogenase II did not react with acetaldehyde dehydrogenase I.Two different strains, A. eutrophus N9A mutant AS1, which represents a different mutant type and can utilize both ethanol or 2,3‐butanediol, and the type strain of A. eutrophus (TF93), which can utilize ethanol, form two acetaldehyde dehydrogenases during growth on ethanol, too. As in AS4, one of these enzymes from each strain amounted to a substantial portion of the total soluble protein in the cells. These major acetaldehyde dehydrogenases were purified from both strains; they resemble acetaldehyde dehydrogenase II isolated from AS4 in all relevant properties. Antibodies against the enzyme isolated from AS4 gave identical cross‐reactions with the enzymes isolated from AS1 and TF93.
Somatic antigens of Pseudomonas aeruginosa
Authors: KNIREL Yuriy A. , PARAMONOV Nikolay A. , VINOGRADOV Evgeny V. , SHASHKOV Alexander S. , DMITRIEV Boris A. , KOCHETKOV Nikolay K. , KHOLODKOVA Elena V. , STANISLAVSKY Evgeny S. 
Published: March 2005

O‐specific polysaccharides, obtained on mild acid degradation of lipopolysacchrides of the serologically related strains Pseudomonas aeruginosa O3 (Lányi classification), O25 (Wokatsch classification) and immunotypes 3 and 7 (Fisher classification), are built up of trisaccharide repeating units involving 2‐acetamido‐2,6‐dideoxy‐D‐galac‐tose (N‐acetyl‐D‐fucosamine), 2,3‐diacetamido‐2,3‐dideoxy‐D‐mannuronic acid or 2,3‐diacetamido‐2,3‐dideoxy‐L‐guluronic acid and 3‐acetamidino‐2‐acetamido‐2,3‐dideoxy‐D‐mannuronic acid or 3‐acetamidino‐2‐acetamido‐2,3‐dideoxy‐L‐guluronic acid. Lányi O3(a),3d,3f and Wokatsch O25 polysaccharides contain also O‐acetyl groups.On the basis of solvolysis with anhydrous hydrogen fluoride, resulting in trisaccharide fragments with N‐acetylfucosamine residue at the reducing terminus, chemical modifications of the acetamidino group (alkaline hydrolysis to the acetamido group or reductive deamination to the ethylamino group), as well as analysis by 1H‐NMR (including nuclear Overhauser effect experiments) and 13C‐NMR spectroscopy, and fast‐atom bombardment mass spectrometry, it was concluded that the repeating units of the polysaccharides have the following structures:

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where HexNAcAmA →α‐L‐GulNAcAmA (∼70%) or β‐D‐ManNAcAmA (∼30%).Lányi O3(a),3d,3f polysaccharide involves two types of repeating units, which differ from each other only in the configuration at C‐5 of the 3‐acetamidino‐2‐acetamido‐2,3‐dideoxyuronic acid residue. Lányi O3(a),3c, O3a,3d,3e and Fisher immunotypes 3 and 7 polysaccharides contain, together with the major repeating units shown above, a small proportion of units in which the derivative of α‐L‐guluronic acid is replaced by the corresponding β‐D‐manno isomer.The data obtained provide the opportunity to substantiate the serological interrelations between these strains of P. aeruginosa by the presence in the O‐specific polysaccharides of common monosaccharides or disaccharide fragments. The distinctions between them stem from the presence or absence of the O‐acetyl group, a different configuration of the glycosidic linkage of the N‐acetylfucosamine residue and/or a different configuration at C‐5 of one or both derivatives of diaminouronic acids.
A kinetic model for lipoxygenases based on experimental data with the lipoxygenase of reticulocytes
Authors: LUDWIG Peter , HOLZHÜTTER Hermann‐Georg , COLOSIMO Alfredo , SILVESTRINI Maria Chiara , SCHEWE Tankred , RAPOPORT Samuel M. 
Published: March 2005

A comprehensive kinetic model for lipoxygenase catalysis is proposed which includes the simultaneous occurrence of dioxygenase and hydroperoxidase activities and is based on the assumption of a single binding site for substrate fatty acid and product.The aerobic reaction of purified lipoxygenase from rabbit reticulocytes with 9,12(Z,Z)‐octadecadienoic acid (linoleic acid) as substrate was studied.The rate constants and the dissociation constants of this enzyme were calculated for the model from progress curves; the model describes correctly the experimental data.The following kinetic features of the reticulocyte enzyme are assumed to apply generally to lipoxygenases. (a) The enzyme shows autoactivation by its product. (b) The rate‐limiting step is the hydrogen abstraction. (c) Both substrate fatty acid and its product are competitive inhibitors of the lipoxygenase. (d) Lowering the oxygen concentration enhances the degree of substrate inhibition, whereas product inhibition is not influenced. (e) If substrate is in excess the oxygen concentration determines the share of dioxygenase and hydroperoxidase activities of the enzyme.As predicted from the model it was found that at low concentrations of oxygen the regio– and stereo‐specificities of the dioxygenation are diminished.During the autoactivation phase the steady‐state approximation does not hold.
Studies on the sequence and structure of the Escherichia coli K‐12 nupG gene, encoding a nucleoside‐transport system
Authors: WESTH HANSEN Svend Erik , JENSEN Nina , MUNCH‐PETERSEN Agnete 
Published: March 2005

The nupG gene, encoding one of the two active nucleoside‐transport systems in Escherichia coli K‐12, has been cloned on the multicopy plasmid pBR322 and derivatives thereof. The recombinant plasmids complemented a chromosomal nupG mutation.A genetic map was determined by digestion with restriction endonucleases and the nucleotide sequence of a 3‐kb stretch of DNA has been determined on fragments cloned into M13 phages. An open reading frame of 1254 bp, encoding a protein with a calculated molecular mass of 45.333 kDa, was deduced to be the coding region of nupG.Minicell‐forming strains carrying plasmids containing this gene were shown to produce a hydrophobic, membrane‐bound polypeptide with an apparent molecular mass of approximately 43 kDa.
Biochemical and immunological evidence for a second nitrate reductase in Escherichia coli K12
Authors: IOBBI Chantal , SANTINI Claire‐Lise , BONNEFOY Violaine , GIORDANO Gerard 
Published: March 2005

Genes different from those of the narGHI operon and encoding a nitrate reductase activity have been cloned by Bonnefoy et al. (unpublished results). We have shown by the use of well‐known assay methods that the encoded enzyme activity is catalyzed by a true nitrate reductase and not by trimethylamine‐N‐oxide reductase or formate dehydrogenase. The biochemical and immunological study, employing anti‐(nitrate reductase) serum raised against the known enzyme, revealed that Escherichia coli contains a second nitrate reductase (nitrate reductase Z) which shares some similarities as well as differences with the known enzyme. By using a strain with a deletion of the narGHI operon and carrying a multicopy plasmid having the nitrate reductase Z genes, we have shown that nitrate reductase Z is a membrane‐bound molybdoenzyme able to couple formate oxidation with nitrate reduction. Like the known nitrate reductase, this enzyme has chlorate reductase activity.The molecular mass and pH and temperature dependence of enzyme Z are similar to these of the known enzyme. On the other hand the two enzymes have significant differences in their electrophoretic mobility on polyacrylamide gels. Unlike the known enzyme, enzyme Z is synthesized in small amounts; the expression of its structural genes does not seem to be induced by nitrate, repressed by oxygen or activated by the product of the fnr gene.The immunological comparison of the two enzymes was performed by rocket immunoelectrophoresis, double diffusion on agar plates and immunoblots. These techniques disclosed a difference between the two enzymes in their recognition by the antiserum and showed that E. coli has two types of nitrate reductase.