bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Arrangement of 18‐S and 28‐S Ribosomal Ribonucleic Acids within the 40‐S Precursor Molecule of Xenopus laevis
Authors: SCHIBLER Ueli , HAGENBÜCHLE Otto , WYLER Tony , WEBER Rudolf , BOSELEY Paul , TELFORD John , BIRNSTIEL Max L. 
Published: March 2005

The arrangement of 18‐S rRNA and 28‐S rRNA within their 40‐S common precursor molecule (pre‐rRNA) of Xenopus laevis was investigated by electron microscopic analysis of secondary structure of nascent pre‐rRNA chains of oocytes, and by 5′‐end analysis of 18‐S rRNA and 28‐S rRNA hybridized to the EcoRI fragment of rDNA cloned as plasmid pCD42.Secondary structure mapping of phenol‐extracted RNA from nucleolar cores revealed complete pre‐rRNA chains of molecules at various stages of processing and pre‐rRNA molecules apparently lacking one end. In this latter group, which was regarded as representing nascent chains, more than 90% of the molecules had no 28‐S rRNA region. This shows that the 28‐S rRNA sequence is transcribed after the 18‐S rRNA region and hence must be located nearer to the 3′ end of the pre‐rRNA molecule.For 5′ end‐group determination [3H]uridine‐labelled 18‐S rRNA and 28‐S rRNA were hybridized, as fragments of about 200 nucleotides. to the plasmid pCD42 containing coding sequences for four‐fifths of the 18‐S rRNA sequence, the external transcribed spacer, the non‐transcribed spacer and a tenth of the 28‐S rRNA sequence. The RNA was recovered from the hybrids and analyzed for uridine 3′,5′‐bisphosphate (pUp) after alkaline hydrolysis. The pUp content of the hybridized 18‐S rRNA fragments was 20‐fold‐higher than in those of 28‐S rRNA, thus demonstrating that the 5′ end of the 18‐S rRNA is located next to the external spacer region.From these results it is concluded that the 18‐S rRNA is located close to the 5′ end of the 40‐S pre‐rRNA molecule.
6‐Methylsalicylic Acid Synthetase from Penicillium patulum
Authors: DIMROTH Peter , RINGELMANN Erika , LYNEN Feodor 
Published: March 2005

The specificity of 6‐methylsalicylic acid synthetase with respect to the priming substrate was studied. If acetyl‐CoA was replaced by propionyl‐CoA 6‐ethylsalicylic acid was synthesized. The rate of this synthesis was about l3% that of 6‐methylsalicylic acid synthesis in presence of acetyl‐CoA.
6‐Methylsalicylic acid synthetase contains an acetyl transferase activity as demonstrated by the transfer of acetyl residues from acetyl‐CoA to pantetheine. This transferase also catalyses propionyl transfer but only with an about 13 times slower rate.
Analogous to fatty acid synthetase, treatment with iodoacetamide converts 6‐methylsalicylic acid synthetase into a malonyl‐CoA decarboxylase. Under certain conditions the iodoacetamide‐treated enzyme could catalyse 6‐methylsalicylic acid formation from malonyl CoA and NADPH without the external addition of acetyl CoA.
Subcellular Distribution and Response to Gastrointestinal Hormones of Adenylate Cyclase in the Rat Pancreas Partial Purification of a Stable Plasma Membrane Preparation
Authors: SVOBODA Michal , ROBBERECHT Patrick , CAMUS Jean , DESCHODT‐LANCKMAN Monique , CHRISTOPHE Jean 
Published: March 2005

The subcellular distribution of adenylate cyclase activity in rat pancreatic homogenates was examined after differential centrifugation. Divalent cations exerted significant effects on this distribution. In addition, the ratio of adenylate cyclase activities in the presence of the C‐terminal octapeptide of cholecystokinin‐pancreozymin and secretin was lower in the crude ‘mitochondrial’ fraction than in ‘microsomal’ fractions. This difference was due to the lability of cholecystokinin‐pancreozymin receptors compared to secretin receptors. The Km app of activation was affected more than the V by this lability. Such a degradation of cholecystokinin‐pancreozymin receptors was markedly delayed by isolation and storage in the presence of a phospholipid mixture.
A simple, reasonably rapid (6 h), and easily reproducible method was developed to prepare a stable semi‐purified plasma membrane fraction, characterized by a 10‐fold increase in the specific activity of adenylate cyclase with respect to the whole homogenate. At variance with data obtained on crude subceilular fractions, the V of adenylate cyclase activity observed in this preparation, under maximal concentration of the C‐terminal octapeptide of cholecystokinin‐pancreozymin, was higher than that obtained with secretin or the vasoactive intestinal polypeptide
The Structural Basis for the Heterogeneity of Chick Down Feather Keratin
Authors: WALKER Ian D. , ROGERS George E. 
Published: March 2005

The amino acid sequences of prominent tryptic peptides of unfractionated carboxymethylated down feather keratin were determined by the dansyl‐Edman procedure and their arrangement within the intact primary structure deduced by comparison with closely homologous components of emu and gull feather keratin. The presence of multiple amino acid interchanges in different down feather keratin chains was inferred. Most or all keratin chains possessed amino‐terminal and carboxyl‐terminal regions, rich in half cystine, and a large internal region devoid of half‐cystine and rich in hydrophobic amino acids. The size of all down feather keratin chains was conserved and the sequence data were compatible with all chains having the same number of amino acid residues.The amino acid substitutions reflected the presence in the chick genome of multiple keratin genes differing from one another by one or a few nucleotide changes.
Antibody to Rheumatoid Synovial Collagenase
Authors: WOOLLEY David E. , CROSSLEY Malcolm J. , EVANSON John M. 
Published: March 2005

An Immunoglobulin G antibody has been isolated from the sera of sheep immunised with purified synovial collagenase obtained from tissue culture medium of rheumatoid synovium.
In double diffusion gels and on immunoelectrophoresis the antibody gave a single precipitin line when run against crude and pure synovial enzyme preparations. Selective adsorption of collagenase from concentrated svnovial tissue culture medium eliminated the precipitin reponse. No immunoprecipitation was observed with whole serum or synovial tissue homogenates in double diffusion gels.
Incubation of immune immunoglobulin G with synovial collagenase resulted in enzyme inhibition and the formation of immunoprecipitates. Fab′ fragments of the antibody were similarly inhibitory but gave no precipitin response. Non‐specific neutral proteinase activity released bysynovial explants was not inhibited by antibody.
Human collagenases derived from gastric mucosa, cornea, and skin were inhibited by the antibody and produced precipitin lines on immunodiffusion showing a reaction of complete identity with the synovial enzyme. Granulocyte collagenase preparations did not react with the antibody.
The non‐human collagenases derived from rabbit cornea and dog gingiva were inhibited by the antibody but those from guinea pig skin and the bacterium Clostridium histolyticum were not. None of these collagenases gave precipitin responses on immunodiffusion against the antibody.
Synovial enzyme preparations inhibited or denatured by chemical reagents retained their capacity to react with the antibody, whereas inhibition by the serum proteins α2‐macroglobulin or β1‐anticollagenase masked the antigenicity of the enzyme as judged by immunodiffusion experiments. These observations and their relevance to the use of the antibody in elucidating the physiological role of collagenase are discussed.
Derivatives of Guanosine Triphosphate with Ribose 2′‐Hydroxyl Substituents
Authors: HAMEL Ernest 
Published: March 2005

This report describes the preparation of four methylated and phosphorylated derivatives of GTP, 2′‐O‐methylguanosine 5′‐triphosphate (PPP‐Me2′Guo), guanosine 2′‐monophosphate 5′‐triphosphate (PPP‐Guo‐2′P), 3′‐O‐methylguanosine 5′‐triphosphate (PPP‐Me3Guo), and guanosine 3′‐monophosphate 5′‐triphosphate (PPP‐Guo‐3′P) These compounds were compared to GTP in their ability to support reactions catalyzed by Escherichia coli initiation factor 2 (IF‐2), elongation factor Tu (EF‐Tu), and elongation factor G (EF‐G).As with previously studied GTI analogues, the nucleotide specificities of IF‐2‐dependent N‐formylmethionylpuromycin formation and EF‐Tu‐dependent Ac‐Phe2‐tRNA formation were similar. There was little difference between the reactions supported by GTP, PPP‐Me 2′ Guo, PPP‐Me3′ Guo, and PPP‐Guo‐3′P, but PPP‐Guo‐2′P was a poor substrate with both enzymes.A spectrum of activity was observed in EF‐G‐dependent formation of N‐acetylphenylalanyl‐phenylalanylpuromycin. While PPP‐Me2′ Guo was almost as effective as GTP in supporting translocation. PPP‐Guo‐2′P was a very poor substrate, having even less activity than guanosine 3′‐di‐phosphate 5′‐triphosphate. Intermediate activities were observed with PPP‐Me3′ Guo and PPP‐Guo‐3′P, the former nucleotide being more active than the latter.
Protein Degradation during Yeast Sporulation Enzyme and Cytochrome Patterns
Authors: BETZ Heinrich , WEISER Ulrike 
Published: March 2005

The levels of several enzymes have been studied during sporulation of Saccharomyces cerevisia. The specific activities of ribonuclease and aminopeptidase I raised several‐fold after transfer of the cells to sporulation medium, whereas the specific activities of phosphofructokinase, glucose‐6‐phosphate dehydrogenase, tryptophan synthase and pyruvate decarboxylase were not significantly altered. The specific activities of NAD‐dependent glutamate dehydrogenase, isoeitrate lyase, malate dehydrogenase and fructose bisphosphatase all decreased from the onset of sporulation. The inactivation of these latter enzymes was inhibited by cycloheximide and by inhibitors of energy metabolism. Hexokinase, alcohol dehydrogenase and glutamate oxaloacetate transaminase were partially lost from the cells during the period of ascus maturation. None of the enzymic changes observed proved to be ‘sporulation‐specific’ in that it occurred exclusively in sporulating diploid yeast cells. Therefore it is postulated that the meiotic events and the metabolic changes required for ascospore formation are under separate genetic control in this organism.During sporulation, the cellular content of cytochromes b, c, and aa3 was reduced to 20% or less of that present in vegetative derepressed cells. Since the relative percentage of total to cycloheximide‐insensitive mitochondrial protein synthesis was not significantly altered throughout sporulation, and the pattern of mitochondrially synthesized polypeptides was rather similar both in vegetative and in sporulating cells, it appeared that not not only degradation but also synthesis and therefore turnover of the mitochondrially coded polypeptides of cytochromes b and aa3 took place during sporulation. The activity ratio of cytochrome c oxidase to F1‐ATPase in submitochondrial particles isolated from vegetative cells and. from purified asci was almost identical. This indicates that the loss of membrane‐bound mitochondrial cytochronies during sporulation is probably due to a nonselective degradation of inner mitochondrial membrane proteins.
The Binding Site of Protein L1 on 23‐S Ribosomal RNA of Escherichia coli
Authors: SLOOF Paul , GARRETT Roger , KROL Alain , BRANLANT Christians 
Published: March 2005

Ribonucleoproteins were prepared by ribonuclease digestion of a reconstituted complex of ribosomal protein L 1 and 23‐S RNA frons Escherichia coli. Three main ribonucleoproteins were identified. The largest was only obtained in an impure state at low ribonuclease concentrations, whereas the two smaller ones, which were difficult to separate from one another electrophoretically, were stable over a range of enzyme concentrations.The two smaller ribonucleoproteins yielded a total of 13 RNA subfragments that were judged to be homogeneous electrophoretically. The latter were characterized for molecular weight and the subfragment composition of each of these ribonucleoproteins was established. Furthermore, the subfragments were shown to be maintained together in each ribonucleoprotein by RNA‐RNA interactionsThe primary and specific binding site of protein L1 was localized on one continuous RNA subfragment of about 110 nucleotides in length by two newly developed binding methods.
The Binding Site of Protein L1 on 23‐S Ribosomal RNA of Escherichia coil
Authors: BRANLANT Christiane , KROL Alain , SRIWIDADA Johannes , EBEL Jean‐Pierre , SLOOF Paul , GARRETT Roger A. 
Published: March 2005

Ribonucleoproteins were obtained by T1 ribonuclease digestion of reconstituted complexes of ribosomal protein L1 and 23‐S RNA From Escherichia coli. The RNA region of the main ribonucleoprotein 2 was totally digested with T 1 ribonuclease. The oligonucleotide products were characterised and they showed that this region comprises 148 nucleotides located between the 550th and 1000th nucleotides from the 3′ end of‐ the 23‐S RNA.Of the other two ribonucleoproteins, the largest ribonucleoprotein 1 contained an extra RNA sequence, of at least 15 nucleotides, that was located at the 5′ end of the RNA region. The smallest ribonucleoprotein 3 lacked an RNA section towards the 3′ end of the region.The order of the RNA subfragments and the enzymic cutting positions in the whole RNA region are given for the ribonucleoproteins. It is shown that protein L 1 most strongly protects a continuous section of‐ 115 nucleotides at the 5′ end of the main RNA region.Finally, evidence is presented for a methylated base, and for two sequence heterogeneities, in this region of the 23‐S RNA.
Studies on 3‐Deoxy‐d‐arabinoheptulosonate‐7‐phosphate Synthetase(phe) from Escherichia coli K12
Authors: SIMPSON Richard J. , DAVIDSON Barrie E. 
Published: March 2005

Investigations with structural analogues of phenylalanine indicated an absolute requirement for the aromatic ring and both the α‐carboxyl and α‐amino groups of phenylalanine for inhibition of 3‐deoxy‐d‐arabinoheptulosonate‐7‐phosphate synthetase(phe) activity. Replacement of the α‐H atom with a methyl group does not decrease the inhibition greatly. Varying degrees of inhibition were observed with o, m and p mono‐substituted fluoro, chloro and hydroxy phenylalanines. ‐d‐Phenylalanine and several metabolites of the aromatic biosynthetic pathways do not inhibit enzymic activity.
Circular dichroism studies indicated that the native enzyme possesses approximately 26%α‐helix. Both circular dichroic and ultraviolet difference spectra indicated that the addition of phenylalanine to the synthetase induces a conformational change involving a small alteration of the secondary structure and large alterations in the interactions of some of the aromatic residues of the enzyme. In particular, a tryptophan residue moves from an extremely hydrophobic environment to one less hydrophobic.
K
d for the binding of phenylalanine to the enzyme was determined spectrophotometrically to he 75 μM.
Chemical modification studies suggested that a sulphydryl group and possibly a lysine residue nay be implicated in the catalytic activity of the enzyme.
Five‐Coordinate Iron‐Porphyrin as a Model for the Active Site of Hemoproteins
Authors: MOMENTEAU Michel , ROUGÉE Michel , LOOCK Bernard 
Published: March 2005

Preparation of iron(III)‐deuteroporphyrin 6(7)‐methyl ester, 7(6)‐(histidine methyl ester) by coupling histidine methyl ester to deuterohemin has been performed using the mixed carboxylic/carbonic‐acid‐anhydride method. This compound, which is very soluble in various organic solvents, can be considered as a prosthetic group model for the active site of five‐coordinate hemoproteins. In the oxidized state a basic, a neutral or an acid form can be isolated. The basic and acid forms are monomeric at all concentrations. The neutral form is found dimeric in concentrated solutions while it is monomeric at low concentrations. The coordination state of iron in these various species is investigated. The neutral form reacts with ligands, such as nitrogenous organic bases, leading to six‐coordinate well‐known hemichromes which exhibit low‐spin electron spin resonance (ESR) spectra. The reaction of anionic ligands, such as F−, CN−, NO2− and N3−, with the neutral form model leads to unsymmetrical six‐coordinate complexes whose optical and ESR spectra are similar to those of synthetic deuteromyoglobin.In benzene, toluene or dichloromethane solutions iron(II)‐deuteroporphyrin 6(7)‐methyl ester, 7(6)‐histidine methyl ester), obtained from ferric forms by heterogeneous reduction with aqueous dithionite, exhibits an optical spectrum characteristic of a five‐coordinate high‐spin ferrous complex. At low temperature important spectral modifications are observed indicating a dimeric association. At room temperature it binds one nitrogenous base molecule leading to the well‐known hemochrome. It reacts also with carbon monoxide with a very high affinity constant (4.5 × 108 M−1), comparable to that of the isolated human hemoglobin α and β chains, but much higher than the values reported for other various models, suggesting that the side‐chain length bearing the fifth ligand may have an important influence upon the reactivity of the sixth position of the iron ion. At low temperature in toluene or dichloromethane, this compound reversibly binds oxygen without oxidation of the iron ion while oxidation occurs at room temperature. The significance of these results is discussed in relation with the local environment, the electronic nature of the base and the immobilization of the heme group in hemoproteins.
A Complex Control Circuit
Authors: THOMAS René , GATHOYE Anne‐Marie , LAMBERT Lucie 
Published: March 2005

Temperate bacteriophages can display in a stable way two essentially different behaviours. In the immune state, a gene (cI) produces a repressor which prevents expression of all the other viral genes; in the non‐immune state the typically viral functions are expressed. The choice between the two pathways and the establishment of one of them have much in common with cell determination and differentiation. This choice depends on a complex control system, in fact one of the most intricate nets of regulation known in some detail. Our paper provides a formal description and partial analysis of this regulatory net. It is shown that even for relatively simple known models, this kind of analysis uncovers predictions which had previously remained hidden. Some of these predictions were checked experimentally.The experimental part chiefly deals with the efficiency of lysogenization by thermoinducible lambda phage carrying mutations in one or more of the regulatory genes, N, cro and cII. Although N− mutations are widely known for preventing efficient integration, and both N− and cII mutations for preventing efficient establishment of immunity, it is shown that, as predicted by a simple model, both N− and cII− phage efficiently lysogenize at low temperature if they are in addition cro−. In contrast with λ N− cro+, λ N− cro− is not propagated as a plasmid at low temperature, precisely because it establishes immunity too efficiently.Genetic control circuits are described in terms of sets of logic equations, which relate the state of expression of genes or of chemical reactions (functions) to input (genetic and environmental) variables and to the presence of gene and reaction products (internal, or memorization variables). From the set of equations, one derives a matrix which shows the stable stationary states (if any) of the system, and from which one can derive the pathways (temporal sequences of states) consistent with the model. This kind of analysis is complementary to the more widely used analysis based on differential equations; it allows one to analyze in less detail more complex systems. The language might be used as well, mutatis mutandis, in fields very different from genetics.The last part of the discussion deals with the role of positive feedback loops in our specific problem (establishment and maintenance of immunity in temperate bacteriophages) and in developmental genetics in general. As a generalization of an old idea, it is suggested that cell determination (for a given character) depends on a set of genes whose interaction constitutes a positive feedback loop. Such a system has two stable stationary states: which one is chosen will usually depend on additional controls grafted on the loop.
Proton Equilibria in the Binding of Zn2+ and of Methylmercuric Iodide to Papain
Authors: SLUYTERMAN Lamoraal A. Æ. , WIJDENES Jacob 
Published: March 2005

The proton liberation on the binding of zinc chloride and methylmercuric iodide to the (essential) thiol group of papain has been examined as a function of pH. This was carried out by (a) direct titration of the protons on the addition of the metal compound to active papain and (b) measurement of the extent of inhibition of enzyme activity by the metal compound as a function of pH.It was found that in the neutral pH range the thiol group or the neighbouring imidazole group in the free enzyme carries one proton, at low pH both groups do so, whereas at high pH neither group carries a proton. The pK values of the free enzyme that govern the proton release, 4.2 and 8.5, correspond to those that govern overall activity. Both from the experiments with methylmercuric iodide and from fluorescence measurements of methylmercuric papain, it was established that the imidazole group in the latter compound exhibits a pK of 5.4. Taking recent data into account, it was considered that the ion pair of thiolate anion and imidazolium cation, proposed by Polgar, is the best approximation to describe the charge distribution in the active centre and to explain the reaction mechanism.
Kinetics of the Interaction between Aspartic Aminotransferase and Anions
Authors: GIANNINI Ivo , BARONCELLI Vittorio , BOCCALON Gianfranco , FASELLA Paolo 
Published: March 2005

The kinetics of the interaction between deionized supernatant aspartic aminotransferase and various anions (cacodylate, phosphate and chloride) were studied by the temperature‐jump technique.The anion concentration in the range covered by our experiments does not affect the transamination rate. On the other hand the conformational transition, recently observed at the active site of the enzyme, is hindered by an excess of anions.A single relaxation effect was observed at the enzyme chromophore wavelength in systems containing the aldimine form of the enzyme and the above anions. It is shown that this effect corresponds to the protonation of the chromophore. The relaxation times were of about 10 μs with phosphate, 20–100 μs with cacodylate and 1–2 ms with chloride. The pH and concentration dependence of this effect were studied. The fits of experimental data to a rate equations for various models were tested by a X2 analysis. The best fit was obtained with models where anions bind rapidly to a site close to the chromophore, so that the pK of the chromophore is affected by anions binding. The rate of the observed relaxation considerably increased when the anion has buffering capacities; this indicates, in the case of cacodylate and phosphate, that the acidic component of the buffer directly exchanges a proton with the enzyme chromophore.