bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on Extrachromosomal DNA Elements
Authors: Goebel Werner 
Published: March 2005

The replication of the colicinogenic factor Col E1 has been studied in two mutants of Escherichia coli with different thermosensitive lesions in DNA replication. One of these mutants E. coli ts 120/6 (Col E1) presumably synthesizes a thermolabile initiator for DNA replication. This mutant is not capable of supporting the synthesis of the Col E1 DNA at the restrictive temperature. The other mutant E. coli ts CR 34/43 (Col E1 DNA at the restrictive temperature at a reduced rate. The Col E1 DNA forms synthesized under the non‐permissive conditions are abnormal. The banding pattern of the DNA in ethidium bromide‐cesium chloride gradients and the sedimentation profile in sucrose gradients suggest that multiple circular and possibly catenated forms of Col E1 DNA are generated under these non‐permissive conditions.Mutant E. coli ts CR 34/43 (Col E1) shows a high colicin production upon induction with mitomycin C at 43°, while mutant E. coli ts 120/6 (Col E1) fails to synthesize colicin at the restrictive temperature.
Conformation du DNA dans la nucléoprotéoprotéine
Authors: Wilhelm F. Xavier , Champagne Madeleine H. , Daune Michel P. 
Published: March 2005

The nucleoprotein of chicken erythrocytes was dissociated by NaCl. The free histone and the residual complex were separated by centrifugation or gel filtration in order to obtain a series of complexes with variable protein content. For each complex the viscosity, circular dichroïsm spectrum and thermal profile were determined and discussed in terms of the configuration and conformation of DNA inside the nucleoprotein.A very small amount of protein is able to provoke a folding of the DNA which then behaves as a rigid rod. Subsequent binding of histones (up to 20—30%) is accompanied by an increased flexibility and a coiled configuration.In the case of a protein/DNA ratio of 0.9, the intrinsic viscosity of the nucleoprotein is four times smaller than the viscosity of DNA in the same condition. Such a decrease could indicate an organization of the DNA in a supercoiled structure.The circular dichroïsm spectrum of the DNA inside the nucleoprotein is very peculiar and bears no resemblance to any known state of DNA (A form or denatured). It is only the positive band between 250 nm and 300 nm which is strongly reduced, the negative one being practically unaffected. Similar results were obtained with solutions of DNA of high salt content.During the progressive stripping of histones the intensity of the positive band remains unchanged with the release of F1 and begins to increase when F2 and F3 are simultaneously liberated.In contrast to this absence of any structural change of DNA with the binding of F1, it is remarkable that the same binding (or release) affects the stability of roughly 50% of the DNA molecule. Although F1 represents about 20% of the total histone, and owing to the cooperative nature of the melting, it seems clear that histones are unequally distributed along the DNA and that F1‐type histones predominantly cover large sequences of nucleotides.
5′‐P‐Forming Exonuclease from Actinomyces sp. of Coelicolor Group, Strain No. 5 (Exonuclease A5) Purification and Some Properties
Authors: Tatarskaya Rachel I. , Lvova Tatyana N. , Abrossimova‐Amelyanchik Nina M. , Korenyako Alexandra I. , Bayev Alexander A. 
Published: March 2005

A new exonuclease named exonuclease A5 has been isolated from the culture medium of Actinomyces sp. of the coelicolor group, strain No. 5 (classification after Krassilnikov). The enzyme exists in the culture broth, as a complex with some other component(s), from which it can be obtained in a free state by non‐ionogenic detergent OP‐7 treatment. Its purification procedure consists of the gel‐filtration of the salted out protein on Sephadex G‐75 and the double chromatography on DEAE‐Sephadex A‐50 at two different pH values. The specific activity of the purified enzyme reaches as a rule 2000 units per mg of protein. The enzyme is free of nucleosidase and deaminase. The nuclease/phosphatase ratio of the best preparations corresponds to 2000—4000. The exonuclease A5 splits RNA and denatured DNA into 5′‐mononucleotides and does not hydrolyze bis‐p‐nitrophenylphosphate. The cleavage begins from the 3′‐end of the polynucleotide chain. The enzyme does not discriminate many modified nucleotides. It hydrolyses T‐even phage DNA as well as tRNA, native or chemically modified. Polynucleotide chains containing no modified bases are split more rapidly however.A peculiarity of the enzyme is its small sensitivity to the 3′‐terminal P. An oligonucleotide with 3′‐terminal P is split with the enzyme into mononucleosidediphosphate (3′‐end), dinucleosidemonophosphate (5′‐end) and 5′‐mononucleotides. Thus the nucleotide sequence of tri‐ and tetranucleotides can be readily established. Dinucleosidemonophosphates are split only with large enzyme amounts. Dinucleotides with 3′‐terminal P are resistant to its attack. The oligonucleotide sequence bearing 5′‐terminal P can be completely split into 5′‐mononucleotides, the last internucleotide bond at the 5′‐end being easily attacked.The above mentioned properties of exonuclease A5 will probably make it useful for determining the nucleotide composition of polynucleotides containing unusual bases, as well as for end analysis of nucleic acid fragments.
Sequence Studies on Bence Jones Proteins
Authors: Alescio‐Zonta Lucilla , Baglioni Corrado 
Published: March 2005

One Bence Jones protein and two Bence Jones fragments (fragmentary chains) of K type, and one Bence Jones protein and two fragments of L type have been analyzed. These proteins have been aminoethylated and digested with proteolytic enzymes. The resulting peptides were separated by different procedures.The peptides obtained were analyzed and could be located in most cases in the amino acid sequence of the corresponding protein by homology with published sequences. These tentative sequences were particularly satisfactory in the case of the three K type proteins. These belonged to subtype KI and showed considerable homologies with other KI proteins. It was more difficult to position peptides of the three L type proteins on the basis of homology with published sequences. Several peptides of one protein (BJ 98) which were completely sequenced by Edman degradation combined with proteolytic digestion could not be positioned.Amino acid analysis of peptides obtained from Bence Jones fragments confirmed that these correspond to the N‐terminal varible region of Bence Jones proteins for K type fragments, whereas they extend for three residues over the C‐terminal constant region for some L type fragments. In any case, no peptide from the constant region of light chains has been isolated from tryptic digests of Bence Jones fragments.
Fatty Acyl Transferase
Authors: Schweizer Eckhart , Lerch Irmgard , Kroeplin‐Rueff Luistraut , Lynen Feodor 
Published: March 2005

A method is described for the isolation of radioactively labeled coenzyme A from yeast which was grown on [1‐14C]pantothenic acid. From about 800 g of wet cells 38 μmoles of chromatographically pure S‐benzoyl‐[14C]coenzyme A were obtained.It was shown that purified yeast fatty acid synthetase catalyzes a fatty acyl transfer reaction between labeled and unlabeled coenzyme A. All saturated fatty acids with chain lenghts between 6 and 18 C‐atoms were transferred at about equal rates. Malonate was transferred about three times faster, acetate, propionate and butyrate about ten times slower than palmitate. Almost no transfer of crotonate and β‐hydroxybutyrate was observed. The transferase was resistant to N‐ethylmaleimide and iodoacetamide inhibition. It is suggested that the binding sites involved in the acyl transfer reactions are the non‐thiol substrate binding sites of the fatty acid synthetase complex, and not the “central” or “peripheral” SH‐groups.Both transferase and total fatty acid synthetase are inhibited by long chain fatty acyl CoA compounds. This inhibition increases with concentration and chain length of the acyl CoA derivative. It is assumed that there is a barrier for the transfer of fatty acids other than acetate from the outer transferase binding site to the active center of the fatty acid synthetase complex, and vice versa. By a local conformational change induced by the end products palmitate and stearate, bound to the “central” SH‐group, this block is released to allow the acids to be transferred from the enzyme to external coenzyme A. Simultaneously, this conformational change is assumed to block further chain elongation.
Localization of Two Species Specific Antigenic Determinants on the Peptide Chains of Calf Skin Collagen
Authors: Pontz Bertram , Meigel Wilhelm , Rauterberg Jürgen , Kühn Klaus 
Published: March 2005

Antibodies against two types of species specific determinants, designated P and S, can be differentiated in rabbit antisera against acid soluble calf skin collagen. Using the passive hemagglutination inhibition technique, they were localized with collagen α‐chains, with peptides obtained by treatment of the α‐chains with cyanogen bromide and with fragments isolated from collagenolytic digests of native collagen.The P‐determinant is labile to proteolytic attack (pronase, chymotrypsin, pepsin). It was detected in a 300 Å region at the C‐terminus of both types of α‐chains. The S‐determinant is resistant to proteases and was found to occur in an interior region of the α2‐chain. The serological activity is contained in one of the collagenolytic peptides.
The Oxidation of Malate by Mitochondria Isolated from Cauliflower Buds
Authors: Macrae Alasdair R. , Moorhouse Ralph 
Published: March 2005

Pyruvate is the major product of malate oxidation by isolated cauliflower bud mitochondria when pyruvate dehydrogenase is inhibited. Pyruvate formation, which requires Mg++, Mn++ or Co++, is stimulated by added NAD.
The effects of ADP, 2,4‐dinitrophenol and respiratory inhibitors on pyruvate formation indicate that the reaction is linked to mitochondrial electron transport.
No enzymic decarboxylation of oxaloacetate to pyruvate by the mitochondria can be observed. With added malate oxaloacetate breaks down in the mitochondria, probably to malate using NADH generated by a mitochondrial malic enzyme.
Acetyl‐CoA and glutamate, which compete for oxaloacetate in the mitochondria, do not inhibit pyruvate formation from malate.
A solubilised NAD requiring malic enzyme is present in sonicates of the mitochondria.
It is concluded that oxaloacetate is not an intermediate in pyruvate formation during malate oxidation by cauliflower bud mitochondria, and that a direct conversion of malate to pyruvate by a mitochondrial NAD requiring malic enzyme occurs.
Préparation de deux fractions d'histones par extraction saline
Authors: Wilhelm F. Xavier , Wilhelm Marcelle L. , Champagne Madeleine H. 
Published: March 2005

A large‐scale procedure for the preparation of two histone fractions by salt dissociation of the chicken erythrocytes nucleoprotein is proposed. The very lysine‐rich histone is selectively removed from the nucleoprotein by NaCl in the range of 0.30 M to 0.55 M and the erythrocytes specific fraction in the range of 0.55 M to 0.80 M. Further purification of the two fractions is achieved by chromatography on a CM‐cellulose column at pH 7. This method enables us to prepare large quantities of these two histone fractions in a relatively short time (3 days). These two proteins are fairly pure as shown by amino‐acid analysis, N‐terminal amino‐acid determination and electrophoresis on polyacrylamide gel.The α‐helical conformation of the two fractions was determined from their optical rotatory dispersion in aqueous and saline solutions. In saline solutions the histones have the highest percentage of α‐helix conformation (20% to 30%).If a comparison is made between the optical rotatory dispersion spectrum of these histones prepared by salt extraction and the optical rotatory dispersion spectrum of the same histones prepared more drastically by acid extraction and precipitation, no difference can be detected in the limit of experimental error. If a two‐term Drude equation is used to analyse optical rotatory dispersion measurements, one can give evidence, especially in the case of the very lysine‐rich fraction, of a structure different from the α‐helix.
Isolation and Characterization of Cyanogen Bromide‐Cleaved Peptides from a Collagenase Digest of α 1‐Chain of Calf Skin Collagen
Authors: Mark Klaus v. d. , Rexrodt Friedrich , Wendt Peter , Kühn Klaus 
Published: March 2005

Molecular fragments of various lengths are formed by treating acid‐soluble collagen with collagenase from Clostridium histolyticum. Fragments 78, 105 and 125 nm long can be isolated by fractional ammonium sulphate precipitation. Their position in the collagen molecule has been determined by electron optical investigations. Denaturation of the individual fragments yielded peptides of the α1‐ and α2‐chains which could be separated by CM‐cellulose chromatography.These peptides, α1 (78) and α1 (105), are in the region of two of those obtained by cyanogen bromide cleavage, namely, α1‐CB7 and CB6; α1 (125) is superimposed on α1‐CB3, CB7 and CB6. In order to obtain smaller fragments of these CB peptides of the α1‐chain, the three fragments from collagenase treatment were cleaved further with cyanogen bromide and the resultant peptides were isolated and characterized. Their position along the α1‐chain was determined electron microscopically after renaturation to the triple helical structure.Each fragment of the α1‐chain yields two chromatographically and electrophoretically distinguishable peptides which have been designated α1 and α1*. The difference between the two was found to reside in the –COOH end of the molecule: the α1* peptide contains seven amino acids more than the α1.
Studies on the Oxidative Fraction of Rabbit Muscle Glyceraldehyde‐3‐phosphate Dehydrogenase
Authors: Cantau Bernard N. , Jaureguiberry Ginette J. , Pudles Julio 
Published: March 2005

In the work presented here, we have examined the most favorable conditions that lead to the isolation of the oxidative fraction of glyceraldehyde‐3‐phosphate dehydrogenase by chymotryptic hydrolysis.NAD+ as well as glyceraldehyde‐3‐phosphate protect the apoenzyme against proteolysis and therefore do not favor the formation of the oxidative fraction. Nicotinamide mononucleotide, and d‐glyceraldehyde modify none of the properties related to the kinetics of proteolysis and do not change the yield in oxidative fraction.Because it oxidizes the sulfhydril groups of the active center of the enzyme, o‐iodosobenzoic acid destroys the protective action of NAD+ with regards to proteolysis, but it also decreases the yield in oxidative fraction.Only AMP has been found to render the apoenzyme more sensitive to chymotryptic digestion and to greatly increase the yield in the oxidative fraction.The effects of glyceraldehyde‐3‐phosphate, NAD+ and AMP on the modification of the arsenolytic activity during chymotryptic hydrolysis have enabled us to determine the dissociation constants of the enzyme for these three effectors.
We have also examined the enzymatic properties of the purified oxidative fraction. Based on the two enzymatic activities retained in the purified oxidative fraction, the following values have been obtained: Km for d‐glyceraldehyde = 61 μM, Km for NAD+= 120 μM, Km for p‐nitrophenylacetate = 6.3 μM.The phosphorylating, phosphatase and NADH‐X activities are absent.As a result of proteolysis, it is possible to dissociate three classes of catalytic functions: (1) the phosphorylating, phosphatase and NADH‐X activities, (2) the oxidative activity and (3) the esterase activity.
Cross‐Linkages in Collagen
Authors: Zimmermann Bodo K. , Pikkarainen Jarmo , Fietzek Peter P. , Kühn Klaus 
Published: March 2005

Three different types of intermolecular bonds were demonstrated to be present in calf collagen.

Side‐to‐side bond: this fixes the quarter staggered array of the molecules within the fibrils and can casily be cleaved by pepsin.
Head‐to‐tail bond: this connects molecules by their dissimilar ends, is located in the region of the 30 nm overlap, and is relatively pepsin resistant.
End‐to‐end bond: this links adjacent molecules by their like ends, is located in terminal regions of the molecules, and can be easily cleaved by pepsin.

Polymeric molecules which were connected solely by end to‐end bonds were extracted from calf skin collagen. Brief treatment with pepsin cleaved side‐to‐side and end‐to‐end bonds in calf Achilles tendon collagen and yielded polymeric molecules which were linked exclusively by head‐to‐tail bonds. Polymeric chains (γ‐ and higher components) were isolated by gel chromatography subsequent to denaturation of end‐to‐end and head‐to‐tail polymers. Polymeric molecules containing the original cross linkages could be reformed by renaturation of these polymeric chains.
Specific Inactivation of Yeast Hexokinase Induced by Xylose in the Presence of a Phosphoryl Donor Substrate
Authors: DelaFuente Gertrudis 
Published: March 2005

Yeast hexokinase can be inactivated by xylose in the presence of MgATP. The effect is highly specific for xylose. The nucleotide and divalent metal specificities are similar to those of the hexokinase reaction. The dissociation constants, as deduced from the effect of the concentration of the inactivating agents on the rate of inactivation, are about 0.2 mM for MgATP and about 10 mM for xylose. These values are similar to the Michaelis constant and Ki value for these compounds as substrate and competitive inhibitor, respectively, in the hexokinase reaction. Sugars capable of binding at the sugar substrate subsite protect against xylose‐induced inactivation with efficiencies closely related to their respective Ks or Ki values. The dissociation constant of glucose, as deduced from its protective effect, is about 0.04 mM.When resting yeast is incubated aerobically with 0.1 M xylose and 1% ethanol, a marked loss of hexokinase activity takes place.Among the possible mechanisms of this irreversible inactivation there is evidence against the involvement of phosphorylation or glycosylation of the protein as well as of a change in its degree of polymerization.
Chorismate Mutase from Euglena gracilis
Authors: Weber Hermann L. , Böck August 
Published: March 2005

One of the key enzymes in the regulation of aromatic acid biosynthesis, chorismate mutase, has been purified about 3000‐fold from cell‐free extracts of Euglena gracilis. The enzyme possesses an apparent molecular weight of 160 000. Judged by our criteria Euglena possesses only one species of chorismate mutase.The purified enzyme is sensitive to inhibition by tyrosine and phenylalanine and to activation by tryptophan; the extent of inhibition and activation is strictly pH‐dependent. The inhibition by phenylalanine and by tyrosine is partially competitive with chorismate. Substrate saturation data of the effector‐free enzyme analyzed by the Hill equation yield values of n of 2.0 at pH 8.4 and of close to 1.0 at pH 7.0, thus indicating strong cooperative interactions under the former and little or no interactions under the latter condition. At pH 7.0 the presence of the inhibitors results in an increase of the value of n suggesting cooperativity under this condition. Little or no cooperative interaction between the inhibitor sites was observed (n′= 1.2). In the presence of tryptophan chorismate mutase exhibits strict Michaelis kinetics (n= 1.0 at pH 7.0 and 8.4).
Study on a Family of Cystine‐Containing Fragments from the Variable Part of Pig Immunoglobulin k‐Chains
Authors: Novotný Jiří , Franěk František , ŠOrm František 
Published: March 2005

From the tryptic hydrolyzate of pig immunoglobulin χ‐chains 6 cystine‐containing fragments were isolated. Amino acid analysis showed that they contained 37–70 amino acid residues and were of a variable nature. There exists a linear relationship between the specific electrical charge of the fragment and the ionic strength of the buffer by which the fragment is eluted from a column of QAE‐Sephadex.Fragments, the disulfide bond of which was split by oxidative sulfitolysis, were split by thermolysin and the hydrolyzates were compared by the method of peptide maps. All the maps of fragments tested contained the peptide Ile‐ThrSer‐CysSSO3‐Arg (where CysSSO3=S‐sulfo‐cysteine) which represents the vicinity of the half‐cystine 24 of pig χ‐chains, as shown by us previously. The nature of the peptide maps indicates that the individual fragments originate in the same section of the primary structure of the N‐terminal half of the χ‐chains. Each of the isolated fragments was a mixture of variants with an identical specific charge but with some amino acid replacements.
Regulation of Gluconeogenesis in the Guinea Pig Liver
Authors: Söling Hans‐Dieter , Wilims Berend , Kleineke Jochen , Gehlhoff Maria 
Published: March 2005

Because of differences in the pattern of enzyme activities involved in glycolysis and gluconeo‐genesis between rat and guinea pig liver, the regulation of gluconeogenesis in guinea pig liver was studied.The following results were obtained:

Starvation increases the capacity for gluconeogenesis from pyruvate in vivo.
Gluconeogenesis from l‐lactate and from pyruvate in isolated perfused livers is greater in the guinea pig than in the rat, whereas gluconeogenesis from other precursors is similar in both species.
Long chain and medium chain fatty acids inhibit gluconeogenesis from l‐lactate in isolated perfused rat liver. In the guinea pig liver the difference does not result from a lower rate of fatty acid oxidation but from a greater reduction in the cytoplasmic NAD+/NADH system.During enhanced fatty acid oxidation in guinea pig liver and in rat liver, similar changes in the concentrations of both acetyl‐S‐CoA and CoA‐SH are observed.With high concentrations of pyruvate as the gluconeogenic precursor, both fatty acids and ethanol lead to a slight stimulation of glucose formation by supplying hydrogen equivalents to the cytosolic NAD+/NADH system.
Both glucagon and dibutyryl‐Ado‐3′:5′‐P stimulate ureogenesis and ketogenesis in isolated perfused guinea pig liver. However, the stimulation of gluconeogenesis by glucagon and Ado‐3′:5′‐P normally observed in isolated perfused rat livers was not found in isolated perfused guinea pig livers.
Partially purified pyruvate carboxylases from rat and guinea pig liver do not differ with respect to the apparent Km values for pyruvate and ATP, and also the apparent Ka values for acetyl‐S‐CoA at different pH values. At constant concentrations of MgATP2− or MnATP2− the pH‐optima for the guinea pig enzyme are significantly lower.
5‐Methoxyindole‐2‐carbonic acid inhibits gluconeogenesis in guinea pig liver in the same way as in rat liver. Quinolinate, on the other hand is far less inhibitory in guinea pig liver and does not inhibit at all in isolated perfused pigeon livers.
Major species differences are found when the activities of the rate limiting enzymes involved in gluconeogenesis are measured under Vmax conditions. Pyruvate carboxylase activity is in the same range in rat and guinea pig liver; pyruvate kinase activity is considerably lower, phospho‐enolpyruvate carboxykinase activity is considerably higher in guinea pig liver.

According to our results gluconeogenesis in guinea pig liver from lactate or pyruvate is mainly regulated by the concentration of pyruvate.The difference in the regulation of gluconeogenesis between rat and guinea pig liver probably results from a difference in the compartmentalization of phosphoenopyruvate carboxykinase. A higher rate of futile cycling between phosphoenolpyruvate and pyruvate in rat liver, due to the higher activity of pyruvate kinase in relation to the activities of phosphoenolpyruvate carboxykinase and pyruvate carboxylase, may also contribute to the observed differences.