bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fast Membrane H+ Binding in the Light‐Activated State of Chromatium Chromatophores
Authors: Chance B. , Crofts A. R. , Nishimura M. , Price B. 
Published: March 2005

A fast and sensitive single‐beam spectrophotometer and a variety of flash and steady‐state illumination sources permit the resolution of bromcresol purple absorbancy changes from background absorbancy changes of Chromatium chromatophores, and identification of these fast absorbancy changes with rapid H+ binding by the chromatophores. A saturating light flash gives a rate several hundred times faster than that obtained in continuous light, the maximal rate being about 50 H+/chlorophyll μsec, with a magnitude of the H+: chlorophyll ratio of 1:30 and a duration for the H+ binding reaction, measured by absorbancy changes of bromcresol purple, of 2.2 msec (half‐time, 800 μsec for a 200 μsec flash). A single turnover flash (10 μsec) yields an H+: chlorophyll value of 1:100, with a duration of the H+ change of 800 μsec and a half‐time of 400 μsec. A double‐flash technique shows the recovery for the fast H+ reaction to have a half‐time of 60 msec. The effects of pH, temperature, uncouplers, and inhibitors are also reported.While the hydrogen ion binding would appear to be closely associated with the reduction of an electron acceptor, Y, particularly on the basis of the similar amounts of the two substances (roughly one each per hundred chlorophyll) the reduction time for Y of 27 μsec is over ten‐fold shorter than the H+ binding time in single flash experiments. In addition, the pH sensitivities and activation energies of the two reactions differ.Thus, either an unidentified electron acceptor is involved in the fast H+ changes, or there is no direct relationship between electron transport and H+ binding. If the latter is the case, we propose that electron transport through the photosynthetic center produces in 800 μsec a state of the membrane (a “membrane Bohr effect”) in which hydrogen ion binding is considerably enhanced.
Magnesium, Potassium, and the Adenylate Kinase Equilibrium
Authors: Blair J. McD. 
Published: March 2005

The influence of magnesium and potassium on the equilibrium catalysed by adenylate kinase has been studied. An equation has been derived which describes the effect of these ions on the equilibrium; values for the metal‐nucleotide stability constants, and for the “true” equilibrium constant, [AMP2−] · [ATP4−]/([ADP3−])2, have been calculated, which give the best fit of this equation to the experimental data.
Using these constants, the concentrations of all significant species in an adenine nucleotide pool equilibrated by adenylate kinase can be calculated, for any specified total concentrations of magnesium, potassium, and adenine nucleotide pool, at any pH and any pyrophosphate bond content of the adenine nucleotide pool. Magnesium emerges as a significant feedback signal from an adenine nucleotide pool considered as an isolated system.
The possible significance of this data with respect to the control of metabolic flux in general and of phosphofructokinase in particular is discussed.
The Metal Complexes of Peptides and Related Compounds
Authors: ÖSterberg Ragnar 
Published: March 2005

The complex formation between copper(I) ions and glycylglycylglycine (H2A+) has been studied in 3.0 M NaClO4 medium at 25° by constant current coulometry using copper amalgam and glass electrodes. In each series of measurements the copper ions were generated into the ligand solution by electrolysis of two phases copper amalgam. The data, shown in Table 2, were treated by graphical methods and by the least squares computer program, Letagrop.It is concluded that the results obtained are consistent by assuming the equilibriaCu++ Cu2++ 2A−⇄ CuICuIIH–3A22−+ 3H+, log β11–32=–3.35 ± 0.04Cu++ A−⇄ CuIA, log β1001= 6.2 ± 0.1 where β is an equilibrium constant.It is assumed that the copper(II)‐equilibria, reported in the previous paper of this series, coexist in solution. On the basis of the equilibrium constants it may be deduced that for pH higher than 6.5 the principal copper(I) complex is CuICuIIH–3A22−. The standard oxidation–reduction potential at pH 7 for the formation of this species from its copper(II) analogue, Cu2H–4A22−, was calculated to be +340 mV.
Tryptophanyl‐tRNA synthétase de pancreas de bœuf
Authors: Cittanova Nicole , Alfsen Annette 
Published: March 2005

A simple and rapid method of obtaining, from beef pancreas, a homogeneous tryptophanyl‐tRNA synthetase without tryptophan, is described. Spectrophotometric and fluorimetric methods have provided new insights into the conformation of the enzyme in absence of substrate.By spectrophotometry, 26 tyrosine groups per mole of enzyme are titrated in the native protein. These chromophores present an abnormally high pK of 11.3 and also have a low accessibility to ethylene glycol and glycerol. In 8 M urea 29 tyrosines are titrated, compared to 36 residues found by amino acid analysis.By spectrofluorimetry, using a fluorescent probe of conformation, 1‐anilino‐8‐naphtalen sulfonate (ANS), we have demonstrated that there is one binding site for ANS per mole of enzyme. The association constant KA= 0.8 × 105 M–1 has been calculated for the complex ANS‐enzyme. The emission wavelength of the complex at 465 nm (instead of 515 nm for ANS in water) suggests a very hydrophobic environment for the bound ANS. The existence of energy transfer between intrinsic chromophores of the protein and ANS is demonstrated. The presence of tryptamine, a competitive inhibitor of the enzymatic reaction, quenches the fluorescence emission of the bound ANS.Although the emission fluorescence of the bound dye is affected by the presence of tryptamine, interpretation of the data demonstrates that the binding of ANS does not occur at the same site as tryptamine. This seems to imply that the catalytic site is not directly involved in the binding of ANS to tryptophanyl‐tRNA synthetase.
The Regulation of Synthesis of Krebs Cycle Enzymes in Neurospora by Catabolite and End Product Repression
Authors: Flavell Richard B. , Woodward Dow O. 
Published: March 2005

Krebs cycle enzymes were repressed in Neurospora during growth on sucrose as carbon source compared with growth on acetate. In mitochondrial, cytochrome‐deficient strains grown on sucrose, this glucose or catabolite repression was reduced. In mutant strains in which protein synthesis and mitochondrial respiration were inhibited, catabolite repression was enhanced. These data support the hypothesis that ATP or the cellular energy level is involved in catabolite repression. The interrelationships between energy metabolism, the energy distribution in the cell and catabolite repression are discussed.The addition of casamino acids to a culture growing on sucrose or acetate, did not cause repression of any of the Krebs cycle enzymes measured, in spite of the fact that many of the constituent amino acids can be considered as biosynthetic products of the Krebs cycle.
The Presence of Both Phage PS8 and Agrobacterium turnefaciens A6 DNA Base Sequences in A6‐Induced Sterile Crown‐Gall Tissue Cultured in vitro
Authors: Schilperoort Robbert A. , van Sittert Nico J. , Schell Jef 
Published: March 2005

The presence of both Agrobacterium tumefaciens and phage PS8 DNA base sequences in sterile crown‐gall tissue grown in vitro was demonstrated by hybridization experiments using crown gall DNA and [3H]RNAs complementary to the bacteria and phage DNAs. These experiments were done under stringent conditions minimizing mismatching of the bases. The approximate amount of A. tumefaciens DNA and PS8 DNA base sequences in crown gall DNA was respectively 9 and 900 genome equivalents. Data are presented indicating that the A6 genome equivalents consist of many copies of a small part of the bacterial genome, while the PS8 genomes are present almost completely. The A6 segment must be large enough to code for four proteins specific for A. tumefaciens present in the crown gall cells and also form a fractional part of the PS8 genome. In cells of the A6 strain used in the experiments no prophage is integrated in the genome of the bacteria. It is postulated that PS8–like DNA is present as a plasmid. Further hybridization‐competition experiments using [3H]cRNA from A. radiobacter showed that one‐third of the A. tumefaciens DNA base sequences in crown gall are also present in A. rudiobacter DNA.No plaque‐forming activity was observed when crown gall tissue homogenates were tested.
Iodoacetic‐Acid‐Resistant Alcohol Dehydrogenase of an Escherichia coli Mutant
Authors: Meyhack Bernd , Pfleiderer Gerhard , Mennigmann H. D. 
Published: March 2005

Nitrosoguanidine‐induced mutants of Escherichia coli were tested in vivo (tetrazolium staining assay) for iodoacetic acid resistance of their alcohol dehydrogenase. One mutant was isolated (mutant 2773) which has a fully iodoacetic‐acid‐resistant alcohol dehydrogenase. Mutant 2773 contains two species of alcohol dehydrogenase; one (the enzyme of the mutant strain, wild‐type fraction i.e. wild‐type‐mutant enzyme) has the same characteristics as the enzyme of the parental strain (wild‐type enzyme), including the inhibition by iodoacetic acid; the other species (enzyme of the mutant strain, mutant fraction i.e. the mutant enzyme) however, is iodoacetic acid resistant, has a high molecular weight (> 600000) and is not related to the wild‐type enzyme as detected by immunological methods.The role of SH‐groups taking part in the reaction at the active center of the alcohol dehydrogenase and the occurrence of several enzyme species are discussed.
An Analysis of the Effects of Oestrogen Treatment in vivo on the Protein‐Synthetic Activity of Male Xenopus Liver Cell‐Free Systems
Authors: Clemens Michael J. , Tata Jamshed R. 
Published: March 2005

A cell‐free protein‐synthesising system has been prepared from the liver of adult male Xenopus laevis which shows several adaptive changes following induction of egg‐yolk protein synthesis by administration of oestradiol‐17βin vivo.
The product of the cell‐free system from oestrogen‐treated animals is characterised by elevated incorporation of radioactive serine relative to phenylalanine. This is taken as an indication of the synthesis of phosvitin, which has a high serine content, in vitro.
Increased protein‐synthetic activity of Xenopus liver ribosomes following oestrogen treatment can be demonstrated and is maintained after the particles are washed in 0.5 M KCl. This effect of the hormone is also apparent when the ribosomes are first stripped of endogenous mRNA by preincubation and then added to a fresh cell‐free system containing poly (U). It is concluded that oestrogen treatment produces an intrinsic activation of synthetic ability of ribosomes in the liver.
Increased ability of ribosomes to translate poly(U) does not result from changes in their ability to bind the polynucleotide, either before or after preincubation.
Cell sap from liver of oestrogen‐treated animals shows increased ability to support amino acid incorporation by ribosomes from control or treated animals in vitro. This is not due to enhanced initiation of peptide synthesis or to increased availability of endogenous aminoacyl‐tRNA in vitro.
The effects of oestradiol on Xenopus liver are considered in relation to the translational control of protein synthesis by hormones and other agents in a variety of systems.
κ (Kappa), a Novel Factor for the Arrest of Transcription in vitro by DNA‐Dependent RNA Polymerase from Escherichia coli at Specific Sites of Natural Templates
Authors: Schäfer Rolf , Zillig Wolfram 
Published: March 2005

A procedure for the isolation of a novel factor, named x, effecting termination or block of transcription of DNAs of bacteriophages T4, T5 and T7 by Escherichia coli RNA polymerase is described.This protein is a dimer of two apparently identical peptide chains, the latter with a molecular weight of about 17000. x is bound to double‐stranded DNA in almost tight packing. It does not influence initiation of transcription. The net rate of RNA synthesis is reduced. The kinetics of transcription in vitro of phage DNAs in the presence of a saturating amount of x lead to a plateau over a wide range of ionic strength. The average chain length of the product at this plateau is 40–50% of that of the product obtained without the factor.The RNA remains bound to the DNA in the blocked end state.Hybridization‐saturation and competition and sedimentation on analysis sucrose gradients yield evidence that the blocking action occurs at a few specific sites of the many x‐binding sites on the DNA.The possible role of this factor is discussed.
Slow Conformational Changes of the Inorganic Pyrophosphatase from Bakers' Yeast Induced by Divalent Metal Ions
Authors: Höhne Wolsfgang E. , Rapoport Tom A. 
Published: March 2005

A study of the role of divalent metal ions, in particular of Mg2+ and Mn2+ in the reaction of the inorganic pyrophosphatase of bakers' yeast has been carried out. It is shown that the free metal ions compete with each other for the same metal binding site. Binding to this site causes reversible conformational changes of the enzyme as indicated by the kinetics. This assumption is in agreement with significant alterations in the circular dichroism spectrum. In the presence of inorganic pyrophosphate the changes of the enzyme are slow enough to be followed kinetically over a period of minutes. Other possibilities for a slow transition of the enzyme velocity which might exist according to the hysteretic enzyme concept of Frieden could be rejected. To explain the experimental data a kinetic scheme is proposed.The results show that, the metal ions affect, the hydrolysis at the substrate site through a conformational change of the protein.
The Induction of Translocators for Di‐ and Tricarboxylic‐Acid Anions inAzotobacter vinelandii
Authors: Reuser Arnold J. J. , Postma Pieter W. 
Published: March 2005

The conditions under which translocators for Krebs‐cycle intermediates can be induced inAzotobacter vinelandiiwere determined. With the exception of mesotartrate andd‐malate, only Krebs‐cycle intermediates themselves are good inducers. Glucose is needed for the induction of a translocator for C4‐dicarboxylic acid anions. Glucose at higher concentrations represses the translocator for C4‐tricarboxylic acid anions. This repression can be released by 3′: 5′‐AMP.Induction of the translocator for C4‐dicarboxylic acid anions probably occurs on the outside of the cell, because intracellularly generated dicarboxylic acid anions do not lead to synthesis of their translocator. Furthermore, contact between the cell and the inducer is necessary only during the first 20–30 min of induction, synthesis of the translaocator going on for another 60 min at least.Induction of a malonate translocator leads to the simultaneous induction of two malonate‐metabolizing enzymes: malonyl‐CoA synthetase and malonyl‐CoA decarboxylase.
Bovine‐Lens Leucine Aminopeptidase
Authors: Lasch Jürgen , Kudernatsch Walter , Hanson Horst 
Published: March 2005

An attempt has been made, by means of kinetic experiments, to get some insight into the molecular mechanism of the binding and catalytic steps taking place during low‐molecular‐weight substrate hydrolysis by leucine aminopeptidase from bovine eye lenses. To this end the variation of the kinetic parameters with concentration and type of well‐known activators (anions and metal cations of valency two) was studied systematically.Additional, we searched for substrate‐like competitive inhibitors. It was found that the end product l‐leucine shows no competition but the compounds N‐p‐tosyl‐N′‐butylcarbamide and N‐sulfanilyl‐N′‐butylcarbamide turned out to be rather potent competitive inhibitors with Ki values comparable to the Km of l‐leucine‐p‐nitroanilide. The variation of the ki values with temperature was studied so that the thermodynamic parameters of inhibitor binding could be calculated.In order to be able to make a meaningful comparison between the kinetic parameters all data were subjected to a computer‐aided (CDC 1604‐A) statistical analysis.
Diacetyl (Acetoin) Reductase from Aerobacter aerogenes
Authors: Johansen Liv , Larsen Sigrun H. , StØRMER Fredrik C. 
Published: March 2005

A kinetic study of diacetyl (acetoin) reductase in the reaction from diacetyl to acetoin has been performed.Product inhibition plots, similar to those obtained for the reduction of acetoin and the reverse reaction, were obtained. The kinetic mechanisms for the reactions catalyzed by the enzyme are proposed.
Diacetyl (Acetoin) Reductase from Aerobacter aerogenes
Authors: Larsen Sigrun H. , Størmer Fredrik C. 
Published: March 2005

The kinetics of the reversible reduction of acetoin and NADH to 2,3‐butanediol and NAD by diacetyl (acetoin) reductase from Aerobacter aerogenes, have been investigated at pH 7.0, 5.8, and 4.8. The reaction follows an ordered bi‐bi mechanism.Acetate acts as an inhibitor of the enzyme with respect to the substrate 2,3‐butanediol. This inhibition increases for decreasing pH, indicating that it is acetic acid that is the effector.These results, in combination with earlier observations, show that high acetate concentration allows maximal 2,3‐butanediol and NAD production at 5.8 from pyruvate and NADH.
Cyanide Binding to Carbonic Anhydrase
Authors: Feeney James , Burgen Arnold S. V. , Grell Ernst 
Published: March 2005

From the similar 13C chemical shifts measured for the cyanide complexes of carbonic anhydrase B enzymes and inorganic zinc cyanide complexes, it is concluded that cyanide binds in its unprotonated form directly to the zinc ion in the enzyme. The cyanide 13C chemical shift of the enzyme · cyanide complex is pH independent indicating that neither the cyanide nor the atom to which it is bonded can undergo protolytic reactions.The 13C spectrum of HCN is reported and the C‐H directly‐bonded coupling constant measured as 275 ± 10 Hz.
The Isolation and Properties of a Tyrosine‐Rich Protein from Wool: Component 0.62
Authors: Frenkel Maurice J. , Gillespie J. Morton , Woods E. Frank 
Published: March 2005

An apparently homogeneous protein (component 0.62), of mol. wt 6900, has been isolated from reduced and carboxymethylated wool proteins by chromatography on QAE‐cellulose at pH 10.5, followed by chromatography on DEAE‐cellulose at pH 8.26% of the amino acid residues of this protein are glycine, another 31% are aromatic amino acids, these together with serine account for 70% of the molecule. The component is unusual in containing no lysine, histidine, glutamic acid, methionine or isoleucine.Electrophoresis in starch gels at pH 8.6 and pH 2.4 and isoelectric focusing in polyacrylamide, indicate that the preparation contains a single component with an isoelectric point of 3.6. Chromatography on calibrated columns of Sephadex G‐75 and Biogel P‐10 gives single symmetrical peaks corresponding in elution volume with an apparent molecular weight of about 4700, whereas ultracentrifugation and sequence give a value close to 7000. It is probable that this discrepancy is due to an extreme retardation of the protein on Sephadex or Biogel due to the large number of aromatic amino acid residues present in the protein. Component 0.62 is almost completely insoluble below pH 9 but increases in solubility with increasing pH and is soluble to the extent of about 0.20% at pH 10.0. This protein component constitutes about 30% of the high‐tyrosine type I protein group and accounts for at least 2% of the mass of fine Merino wools.
The Primary Structure of an Acidic Protein from 50‐S Ribosomes of Escherichia coli which is Involved in GTP Hydrolysis Dependent on Elongation Factors G and T
Authors: Terhorst Cox , Möller Wim , Laursen Richard , Wittmann‐Liebold Brigitte 
Published: March 2005

The primary structures of the ribosomal proteins A1 (= L7) and A2 (= L12) have been elucidated. Comparison of the two amino acid sequences confirms earlier studies by us (1972) which indicated that the two proteins are identical except that A1 possesses an N‐terminal acetyl group.Sequencing of tryptic and chymotryptic peptides was accomplished primarily by automatic solid‐phase Edman degradation of 50‐ to 70‐nanomole peptide samples. A large tryptic peptide T1Phe, which could not be sequenced by this method, was fragmented with elastase and its sequence mainly derived by conventional methods. The sequence of the first 51 residues of the nonacetylated A2‐protein was obtained by Edman degradation in the Beckman sequencer.A‐protein comprises three distinct regions: I (residues 1—55), which is negatively‐charged and hydrophobic, II (56—81), which is positively charged, and III (82—120), which is negatively charged and hydrophilic. α‐Helix promoting residues are located primarily in regions I and III. ɛ‐N‐Monomethyllysine, which occurs in 50% of the A1 and A2 chains is located in the more flexible region II at position 81.The distinctive clustering of hydrophobic and charged residues is quite remarkable and suggests that in situ certain of these regions may contain a binding site for components involved in peptide chain elongation.
Spectrophotometric Studies on the Interaction of Sarcoplasmic‐Reticulum Fragments with Adenosine Triphosphate and Calcium
Authors: Nakamaru Yoshiaki , Schwartz Arnold 
Published: March 2005

An interaction of sarcoplasmic reticulum of skeletal and cardiac muscle with bromeresol purple was studied in the absence and presence of ATP and/or calcium using dual‐wavelength spectrophotometry.
In the absence of added calcium, addition of ATP induced four specific phases that were measured as successive changes in absorption intensity of bromeresol purple at the wavelength pair 590—600 nm: phase 1, rapid decrease; phase 2, rapid increase; phase 3, gradual decrease; and phase 4, gradual increase.
The absorption intensity of the phases was entirely reversed in direction at the wavelength pair 615—640 nm. The wavelength of maximum absorption by bromeresol purple was 587 nm; the isosbestic point with respect to pH was 488 nm.
At the wavelength pair 488–540 nm and in the presence of ATP, phase 2 and phase 4 were not observed. The intensity‐increasing phase was completely calcium‐independent and represented a blue shift of the absorption spectrum of bromeresol purple.
The intensity‐decreasing phase was calcium‐dependent and included both a red shift and some pH changes of the medium. The blue shift (phase 2) accompanied the interaction of sarcoplasmic reticulum, ATP and magnesium.
Addition of calcium caused a shift back to longer wavelengths (phase 3). The initiation of the blue shift (phase 2) coincided with removal of calcium in the medium by active accumulation. Calcium had no effect on the shift in the absence of ATP.
The results suggest that the blue shift (shift to shorter wavelengths, phase 2) might reflect the formation of a sarcoplamic reticulum · ATP complex; the red shift (to longer wavelengths, phases 1 and 3) might reflect conversion of this complex to another intermediary form.