Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Angiotensin has previously been shown to inhibit distal renal tubular sodium reabsorption. As a consequence of this, or independently, it might influence the distal handling of other electrolytes. We have therefore examined the effects of angiotensin on the distal reabsorption or secretion of a spectrum of electrolytes. 2. Standard bilateral stop-flow studies were done on anaesthetized, adrenalectomized rabbits, in which the effects of intravenous infusions of either 0-02-0-05 mug min-1 kg-1 or 1 mug min-1 kg-1 of angiotensin were compared with control stop-flow results. 3. The lower dose of angiotensin inhibited distal sodium, chloride, water and magnesium reabsorption, inhibited distal hydrogen secretion and stimulated distal potassium secretion. The higher dose of angiotensin produced these changes and additionally inhibited distal calcium reabsorption. Most of the observed changes were dose-related. The low dose of angiotensin did not significantly raise blood pressure but the high dose was pressor. 4. Changes in the stop-flow patterns induced by the higher dose of angiotensin were compatible with, and may help to explain, the changes it produced in urinary excretion of sodium, chloride, potassium, magnesium and calcium in clearance studies before stop-flow. Suppression of hydrogen secretion caused by both doses of angiotensin in the stop-flow studies was also reflected by reductions in acid excretion produced by these infusion rates in additional experiments performed by clearance methods in acid-loaded, conscious rabbits. 5. The results support the view that angiotensin may have an important intrarenal role, at least in rabbits.
Clin Sci Mol Med 1976 Feb
PMID:Multiple changes in distal stop-flow electrolyte patterns and reduction of acid excretion induced in rabbits by angiotensin. 0 4

1. Seven healthy males were studied during cycle ergometer exercise at 33%, 66% and 90% of VO2 max. on three occasions when NH4C1, NaHCO3 or CaCO3 (as a control substance) were administered in gelatin capsules double blind and in randomized order. Plasma growth hormone (HGH), lactic acid and hydrogen ion concentration ([H+]) were measured at frequent intervals. 2. Ammonium chloride produced highest blood [H+] and NaHCO3 the lowest. These differences were maintained during exercise and in recovery. Plasma lactic acid concentrations were similar at rest. At 66%, 90% VO2 max. and recovery lactic acid was highest with NaHCO3 and lowest with NH4C1. 3. Exercise stimulated HGH secretion in all studies and the elevation was proportional to the intensity of the exercise. NH4C1 caused a variable elevation of HGH at rest and 33% VO2 max. At 66% VO2 max., plasma HGH was significantly elevated to similar concentrations in all studies and, at 90% VO2 max., HGH was highest with NaHCO3. 4. An infusion of sodium L(+)-lactate producing plasma lactate concentrations of 3-5 mmol/l did not influence HGH secretion. 5. Exercise is a physiological stimulus to HGH secretion and the mechanism is independent of blood [H+] and lactate concentrations.
Clin Sci Mol Med 1976 Apr
PMID:Growth hormone secretion in acid-base alterations at rest and during exercise. 0 58

Incubation of CMP in 2H2O with 0.5M cysteine methyl ester at p2H 5 and 37 degrees C for 24 h resulted in 43% exchange of 5-H to 5-2H. No deamination of the cytosine nucleus was noted during this treatment. Native and denatured DNA samples from calf thymus were treated in 3H2O with cysteine methyl ester at pH 5 and 37 degrees C for 24 h and incorporation of tritium into each DNA base was determined by enzymic digestion of the treated DNA. The order of the specific radioactivity found was cytosine greater than guanine greater than adenine greater than thymine for denatured DNA and guanine greater than adenine approximately cytosine greater than thymine for native DNA. The ratio of radioactivity for denatured/native was 11.6 for cytosine, 1.5 for guanine, 1.8 for adenine and 1.1 for thymine. Hence the incorporation in cytosine under the reaction conditions is preferential for single-stranded, nonhelical regions of DNA. Escherichia coli glutamic acid tRNA II was treated in 3H2O with 1.24 M cysteine methyl ester at pH 5 and 37 degrees C. The 24-h-treated tRNA was digested with ribonuclease T1 and the fragments were fractionated. Each fragment was then digested with ribonuclease T2 into mononucleotides and the radioactivity distribution among the bases was determined. The average radioactivity found for each of the bases of the four major nucleotides was cytosine greater than guanine approximately adenine greater than uracil. The radioactivity in cytosine varied greatly among the RNase T1 fragments, the ratio of the highest to the lowest radioactivity being 18.7. The corresponding value for guanine was 11.1, for adenine 4.73 and for uracil 3.64. Based on the data obtained, it was deduced that in this tRNA the anticodon loop, the dihydrouridine loop and the extra loop were "exposed" under the conditions employed for the labeling. The 5'-terminal cytosine of the anticodon loop was in a "non-exposed" state, a situation similar to that previously reported for E. coli tyrosine tRNA [Cashmore, A. R., Brown, D. M. & Smith, J. D. (1971) J. Mol. Biol. 59, 359-373] and for E. coli formylmethionine tRNA [Goddard J. P.+Schulman L. H. (1972) J. Biol. Chem. 247, 3864-3867]. Both cytosine 48, located at the 3'-terminal of the extra loop, and guanine 15 in the dihydrouridine loop were in an "emposed" state. This finding does not agree with a tRNA model in which this pair of cytosine and guanine, commonly found in tRNA sequences, forms hydrogen bondings. Positions 30--32, 61--64 and 71, which are located in the stems, were found to be strongly "buried".
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PMID:Conformation of Escherichia coli glutamic acid tRNA II as studied by hydrogen-tritium exchange catalyzed by cysteine methyl ester. 0 69

1. Intracellular hydrogen ion activity, [H+]i, was extimated in human erythrocytes and in nucleated avian erythrocytes from measurements of the distribution of ammonia and 5,5'-dimethyloxazolidine-2,4'-dione (DMO) between intracellular and extracellular fluid. 2. In human erythrocytes there was no difference between values for [H+]i derived from measurements of either DMO or ammonia. 3. In avian erythrocytes, [H+]i(ammonia) was consistently greater than [H+]i(DMO), indicating significant acid-base heterogeneity of the intracellular water. The degree of heterogeneity was assessed by reference to a theoretical model of two compartments of equal size. 4. Experiments with nuclei isolated from avian erythrocytes suggested that DMO is not bound to nucleoproteins, and that the nucleus may be more acidic than the cytoplasm.
Clin Sci Mol Med 1976 Aug
PMID:Intracellular acid-base heterogeneity in nucleated avian erythrocytes. 0 34

The equilibrium constant of a complex of tRNA with the 50S ribosomal subunit was measured in the absence of a template. It was shown that the stability of the complex increases with an increase in the concentration of Mg2+, it decreases with an increase in the concentration of univalent ions, and does not depend on the pH of the medium in the range of 7.0-8.2. Removal of the 3'-terminal nucleoside of tRNA weakens the association approximately 40-fold; the subsequent successive splitting off of another three nucleotides has little effect on the association constant. In 90% 2H2O the stability of the complex increases approximately four-fold, which points to the large contribution of the hydrogen bonds to the free energy of the interaction. The tetranucleotide TphiCG competes slightly with tRNA for sites on the 50S subparticles; this means that the TphiC segment of tRNA does not play an important role in the formation of the complex under investigation.
Mol Biol (Mosk)
PMID:Interaction of transfer RNA with 50S ribosomal subunits of Escherichia coli in absence of templates. 1 9

pH-Induced helix-random coil transitions in random copolymers of Ala with Glu have been investigated in order to determine the effect of Ala on the stability of the helical state of polyglutamic acid. The free energies for the transfer of one uncharged Glu residue from a random coil to a helix (deltaGo) have been determined from potentiometric titration curves by the method of Zimm and Rice. It has been shown that the introduction of Ala hampers the transfer of a Glu residue from a random coil to a helix (reduces -deltaGo), although Ala itself is a helix-forming residue, i.e., its free energy decreases during helix formation. This has suggested that its introduction weakens the helix-stabilizing interactions between the uncharged Glu residues (apparently hydrogen bonds). The evaluation of the intrinsic helix-random coil equilibrium constant s for uncharged Glu residues with consideration of this situation yields a value which is smaller than the value of s for (Glu)n and in good agreement with the theoretical values.
Mol Biol (Mosk)
PMID:Thermodynamic parameters of helix-random coil transitions in polypeptide chains. IV. Random copolymers of L-alanine with L-glutamic acid. 1 14

According to the data of many physical and physico-chemical methods for conditions near to physiological, there are two types of spontaneous reversible conformational transitions in native proteins namely, local transconformations and overall unfolding of the molecule. Conformational transitions of both types occur with correlation times of less than 10-1--10-3 sec. Some local transconformations, especially those revealed by the hydrogen exchange method, are characterized by weak temperature dependence of the equilibrium constant (local temperature-independent (TI) transconformations). Combining the data obtained by the hydrogen exchange method with recently published results of energy refinement of protein structure leads us to suggest that the probability of local TI-transconformations is independent of hydrophobic forces and possibly related to the "internal" conformational free energy of the native protein, i.e. the sum of (1) the potentional energy of non-bonded intramolecular interactions, (2) the energy of dihedral and bond angle strain as well as (3) the entropy of the folded protein. In the proposed model of dynamic structure the cooperative nature of local TI-transconformations is a result of close interrelation between the optimization of van der Waals side chain interactions in the nonpolar core and variation of dihedral and valence angles. It is shown that the local TI-conformers are closely related to the functionally important transient key states of native proteins.
Mol Biol (Mosk)
PMID:[Equilibrium dynamics of the 3-dimensional structure of globular proteins]. 2 3

Forward and reverse reactions of catalysis by a hydrogenase from T. roseopersicina in steady state have been investigated. The dependance of reaction rate on the concentration of substrates and of hydrogen ions has been studied. Detailed formal-kinetic analysis of possible mechanisms of enzyme action has been carried out and the classification of mechanisms of the reaction has been given. Comparison of experimental data with the equations obtained from formal-kinetic analysis has been undertaken and mechanisms compatible with experimental data were sorted out. Kinetic and molecular mechanism of the catalytic activity of hydrogenase has been proposed and elementary rate constants for the activation of molecular hydrogen have been calculated.
Mol Biol (Mosk)
PMID:[Stationary kinetics of catalysis by the hydrogenase of Thiocapsa roseopersicina]. 2 4

Reversible unfolding of bovine chymotrypsinogen A in 2H2O either by heating at low pH or by exposure to 6 M guanidinium chloride results in the exchange of virtually all the nitrogen-bound hydrogens that give rise to low-field 1H NMR peaks, without significant exchange of the histidyl ring Cepsilon1 hydrogens. These preexchange procedures have enabled the resolution of two peaks, using 250-MHz correlation 1H NMR spectroscopy, that are attributed to the two histidyl residues of chymotrypsinogen A. Assignments of the Cepsilon1 hydrogen peaks to histidine-40 and -57 were based on comparison of the NMR titration curves of the native zymogen with those of the diisopropylphosphoryl derivative. Two histidyl Cepsilon1 H peaks were also resolved with solutions of preexchanged chymotrypsin Aalpha. The histidyl peaks of chymotrypsin Aalpha were assigned by comparison of NMR titration curves of the free enzyme with those of its complex with bovine pancreatic trypsin inhibitor (Kunitz). The NMR titration curves of histidine-57 in the zymogen and enzyme and histidine-40 in the zymogen exhibit two inflections; the additional inflections were assigned to interactions with neighboring carboxyl groups: aspartate-102 in the case of histidine-57 and aspartate-194 in the case of histidine-40 of the zymogen. In bovine chymotrypsinogen A in 2H2O at 31 degrees C, histidine-57 has a pK' of 7.3 and aspartate-102 a pK' of 1.4, and the histidine-40-aspartate-194 system exhibits inflections at pH 4.6 and 2.3. In bovine chymotrypsin Aalpha under the same conditions, the histidine-57-aspartate-102 system has pK' values of 6.1 and 2.8, and histidine-40 has a pK' of 7.2. The results suggest that the pK' of histidine-57 is higher than the pK' of aspartate-102 in both zymogen and enzyme. A significant difference exists in the structure and properties of the catalytic center between the zymogen and activated enzyme. In addition to the difference in pK' values, the chemical shift of histidine-57, which is highly abnormal in the zymogen (deshielded by 0.6 ppm), becomes normalized upon activation. These changes may explain part of the increase in the catalytic activity upon activation. The 1H NMR chemical shift of the Cepsilon1 H of histidine-57 in the chymotrypsin Aalpha-pancreatic trypsin inhibitor (Kunitz) complex is constant between pH 3 and 9 at a value similar to that of histidine-57 in the porcine trypsin-pancreatic trypsin inhibitor complex [Markley, J.L., and Porubcan, M. A. (1976), J. Mol. Biol. 102, 487--509], suggesting that the mechanisms of interaction are similar in the two complexes.
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PMID:Zymogen activation in serine proteinases. Proton magnetic resonance pH titration studies of the two histidines of bovine chymotrypsinogen A and chymotrypsin Aalpha. 3 98

Concentration dependence of the equivalent conductance of isoionic DNA solutions has been studied at different temperatures. The limiting equivalent conductance (lambda infinity) at every temperature investigated has been obtained by extrapolation to the infinite dilution in Kohlraush's plots. At the same time in plots c lambda c versus 1/lambda c (lambda c is equivalent to conductance at the concentration c), corresponding to the linear form of Ostwald's dilution law, the straight lines were obtained. Both lambda infinity and acidity constants (K) have been determined from these plots. The values of lambda infinity by two methods are in well agreement. The average values of lambda infinity were used for energy activation of conductivity calculation, equal to 2,40 +/- 0,05 kcal/mole. The acidity constant of primary phosphoryl groups passes through a maximum near 33 degrees. Equivalent conductance of hydrogen ions calculated by neglecting of macroion's mobility and by using of potentiometric determined concentration (cH+) has been shown to increase with cH+. Unusual behavior of DNA in isoionic solutions is discussed.
Mol Biol (Mosk)
PMID:[Temperature dependence of conductance of isoionic DNA solutions. Determination of dissociation constants of primary phosphoryl groups]. 3 37


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