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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The absence of summation of the rate of methylation of positionally analogous cytidine residues in tRNA1Val, tRNAPhe, and tRNAMet in the case of simultaneous presence of two substrates in the incubation mixture was demonstrated by the method of mixed substrates. The same result was also obtained in the methylation of A19 (counting from the 3' end of the molecule) in tRNA1Val, tRNAPhe, tRNAfMet, tRNASer, and tRNAGlu individually and in the case of their mixing in pairs. These data are evidence that positionally analogous nucleotides in different RNAs are attacked by the same enzyme. Yeast tRNASer, already possessing a methyl group at the cytidine residue studied, proved to be an effective inhibitor of methylase, forming m5C with valine and phenylalanine tRNAs. The results obtained are evidence that differences in the primary and secondary structures at the site of methylation are not the deciding factors in the interaction of tRNA with methylases.
Mol Biol (Mosk)
PMID:Use of the method of mixed substrates to study the specificity of tRNA methylases. 79 57

1. The characteristics of absorption of individual amino acids from amino acid mixtures simulating casein and from enzymic hydrolysates of casein containing oligopeptides as well as free amino acids are known to be different. The differences, which are attributable to mucosal uptake of small peptides, involve more rapid absorption from the enzymic hydrolysates of certain amino acids which are relatively slowly absorbed from the amino acid mixtures. This could lead to more effective utilization of amino acids from the enzymic hydrolysates than from the amino acid mixtures. 2. To obtain further information bearing on this hypothesis, we have used a recently developed technique for portal cannulation in the guinea pig to make a preliminary investigation of amino acid concentrations in the portal venous plasma at intervals after the infusion into the duodenum of equivalent amounts of (a) an amino acid mixture simulating casein and (b) a partial enzymic (papain followed by kidney peptidases) hydrolysate of casein, the two preparations being infused in separate experiments. 3. For some amino acids, such as leucine, isoleucine, valine, phenylalanine and lysine, the curves after the enzymic hydrolysate were fairly similar to the corresponding curves after the amino acid mixture, though usually slightly lower. With other amino acids, the curves after the enzymic hydrolysate were very much lower than the corresponding curves after the amino acid mixture. With serine, glutamine, proline and glycine this discrepancy was particularly great. 4. The results cannot yet be fully explained, but their main features are explicable by the hypothesis that the lower amino acid concentrations in portal plasma after the enzymic hydrolysate are the result of entry of amino acids into the portal blood in peptide form, in which they would not be detectable by the analytical technique employed, and possibly also of more rapid clearance of amino acids from the blood during absorption of this preparation.
Clin Sci Mol Med 1977 Mar
PMID:Amino acid concentrations in portal venous plasma during absorption from the small intestine of the guinea pig of an amino acid mixture simulating casein and a partial enzymic hydrolysate of casein. 84 57

1. We have compared the effect of central and peripheral administration of angiotensin II and (1-succinamoly-5-valine-8-phenylglycine)angiotensin II on blood pressure of male conscious unrestrained rats with normal blood pressure, and with spontaneous hypertension or chronic renal hypertension. 2. After central and peripheral injection of angiotensin II all rats exhibited a significant dose-related increase in blood pressure. 3. Administration of the analogue was without effect in normotensive rats. Ten-weeks-old rats with spontaneous hypertension showed a significant blood pressure decrease after central injection, but an increase after peripheral injection. This centrally induced decrease could not be observed in spontaneously hypertensive rats 14 weeks old. In these animals the analogue increased the blood pressure. In rats with chronic renal hypertension in contrast to peripheral injection, central administration decreased the pressure significantly. 4. Plasma renin activity was not changed after central injection of the analogue in normotensive rats. 5. These observations suggest the participation of the intrinsic brain isorenin-angiotensin system in central blood pressure regulation in these forms of experimental hypertension.
Clin Sci Mol Med Suppl 1976 Dec
PMID:Blood pressure response to central and peripheral injection of angiotensin II and 8-C-phenylglycine analogue of angiotensin II in rats with experimental hypertension. 107 54

Hybridization of messenger ribonucleic acid (mRNA) isolated from Escherichia Coli K-12 to deoxyribonucleic acid (DNA) from lambdaCI857st68h80dilv was used to detect isoleucine-valine (ilv) specific mRNA. A number of strains partially constitutive for the isoleucine-valine enzymes had levels of ilv mRNA 2 to 3-fold higher than the parent strain. Starvation for any of the branched-chain amino acids resulted in a 20 to 23-fold increase in ilv mRNA as compared to repressed levels. These differences were not due to altered growth rates or to changes in the stability of ilv mRNA. These data indicate that regulation of the isoleucine-valine enzymes by multivalent repression occurs mainly at the level of transcription. Kinetics of elongation of ilv mRNA after repression are consistent with the assumption that the mechanism of multivalent repression involves the prevention of further initiations by RNA polymerase.
Mol Gen Genet 1975 Jun 19
PMID:Transcriptional control of the isoleucine-valine messenger RNA's in E. coli K-12. 110 33

Cationic amino acids, arginine and lysine partition differentially from water into aqueous micellar sodium dodecanoate. Conversely, partitioning of serine, glycine, aspartic acid, glutamic acid, threonine, alanine, proline, valine, leucine, phenylalanine and isoleucine do not vary appreciably. Partitioning from neat hexane into dodecylammonium propionate trapped water in hexane is, however, dependent upon both electrostatic and hydrophobic interactions. These results imply that the interior of dedecylammonium propionate aggregates is negatively charged and is capable of hydrogen bonding in addition to providing a hydrophobic enviroment. The solubilities of amino acids in neat hexane substantiate the previously derived amino acid hydrophobicity scale. Relevance of partitioning in these systems to the postulated selective amino acid compartmentalization is discussed.
J Mol Evol 1975 Nov 04
PMID:Compartmentalization of amino acids in surfactant aggregates. Partitioning between water and aqueous micellar sodium deodecanoate and between hexane and dodecylammonium propionate trapped water in hexane. 120 27

We have used the chemical cleavage mismatch technique to screen for mutations in the cystic fibrosis gene. Analysis of exons 10 and 11 in the first nucleotide binding fold led to the detection of several described mutations and two novel mutations, V520F and C524X. V520F results from a G-->T nucleotide substitution changing a valine to a phenylalanine residue, while C524X (a nonsense mutation), results from a C-->A transversion. A third novel mutation, Q1291H (G-->C), at the last nucleotide of exon 20, would substitute a histidine residue for glutamine. Further study, involving RNA based PCR, revealed that Q1291H was also a splice mutation. Both correctly and aberrantly spliced mRNAs are produced from the Q1291H allele. The incorrectly spliced product results from the use of a nearby cryptic splice site 29 bases into the adjacent intron.
Hum Mol Genet 1992 Apr
PMID:Three novel mutations in the cystic fibrosis gene detected by chemical cleavage: analysis of variant splicing and a nonsense mutation. 128 66

The mutation of valine 188 to leucine in the viral protein 1 of human rhinovirus 14 renders the virus resistant to certain antiviral compounds. Thermodynamic-cycle perturbation theory provides a means of calculating the difference in the binding free energies of an antiviral compound to the wild-type virus and to the mutant virus. In calculating the relevant free-energy differences in molecular dynamics simulations, it is important to sample the multiple rotational isomers of residue 188 correctly. In general, these rotamers will not be fully sampled during a single molecular dynamics simulation. However, the contributions of all the rotamers to the free-energy differences associated with mutation of residue 188 may be considered explicitly once they have been identified and their relative free energies determined. Therefore, we describe here the mapping of the rotamers of residue 188 by steric-bump search and energy minimization techniques, and by the computation of potentials of mean force (p.m.f.s.) using umbrella sampling. The usefulness, validity and efficiency of these methods of examining rotameric states is discussed. Adiabatic mapping by energy minimization was found to be unreliable for this residue due to the small magnitude of its interactions with the surrounding protein atoms. Ambiguities in the adiabatic maps were resolved by computing p.m.f.s. The p.m.f. for valine 188 in the unliganded wild-type virus shows a minimum corresponding to the crystallographically observed conformation of valine 188. The p.m.f.s. for valine 188 in the liganded virus and for leucine 188 in the unliganded mutant virus suggest that the experimentally observed conformations may be interpreted as averages of a number of conformations corresponding to those at the minima in the p.m.f.s. The calculations suggest also that the conformation of leucine 188 may change when the ligand binds. The use of the calculated p.m.f.s. to compute the difference in the free energy of binding of an antiviral compound to the wild-type and mutant rhinoviruses is described in the accompanying article.
J Mol Biol 1992 Jun 05
PMID:Binding of an antiviral agent to a sensitive and a resistant human rhinovirus. Computer simulation studies with sampling of amino acid side-chain conformation. I. Mapping the rotamers of residue 188 of viral protein 1. 131 83

Thermodynamic-cycle perturbation theory and molecular dynamics simulations were used to calculate the difference in the free energy of binding of the antiviral compound WIN53338 to the wild-type human rhinovirus 14 and to a drug-resistant mutant of the virus in which valine 188 of the viral protein 1 is mutated to leucine. Because of the difficulty of achieving adequate sampling of all of the rotational isomers of amino acid side-chains in molecular dynamics simulations, an explicit treatment of the effects of the existence of multiple rotational isomers of residue 188 on the calculated free energies was used. The rotamers of residue 188 were first mapped by steric and energetic techniques as described in the accompanying article. Thermodynamic integration was then carried out during simulations of the virus, both with and without the antiviral compound bound, by mutating residue 188 while restraining its side-chain to one conformation. The contributions of the other rotamers of residue 188 to the free-energy changes for this mutation were then added to those calculated by thermodynamic integration as correction factors. Binding of WIN53338 to the wild-type virus was calculated to be favored over binding to the mutant virus by 1.7(+/- 3.0) kcal/mol. This is consistent with experimental data which, if differences in activity are assumed to be due to differences in binding, indicate that the binding affinity of WIN53338 for the wild-type virus is at least 0.15 to 1.7 kcal/mol greater than for the mutant virus. Thermodynamic integration was also performed in the conventional manner without restraints and was found to give less accurate results.
J Mol Biol 1992 Jun 05
PMID:Binding of an antiviral agent to a sensitive and a resistant human rhinovirus. Computer simulation studies with sampling of amino acid side-chain conformations. II. Calculation of free-energy differences by thermodynamic integration. 131 84

The molecular conformation of ubiquitinated structures and the validity of the N-end rule were examined by simulating the molecular mechanics to ascertain the global energy-minimized structure. We examined the chemical linkage involved in attaching the ubiquitin carboxyl terminus to the N-terminus of three different x-hexapeptides, where x is the amino group of the acceptor peptide--either valine, arginine or glutamic acid--(x-K linkage) and to the epsilon-amino group of lysine of the acceptor hexapeptide x-glu1-his2-lys3-gly4-lys5-val6 (K-K linkage) through the formation of an isopeptide bond. Changes in conformation and molecular stability of the multi-ubiquitinated structures were determined by energy-minimization procedures using the SYBYL program developed by Tripos Associates. In the x-K linkage, the ubiquitin molecule is stretched in the beta-pleated sheets and beta-turns while the alpha-helices expand, as the molecule continues to unfold linearly. In the K-K linkage, the ubiquitin molecules have turned into a u-shaped, semi-circular alignment, contracting into a compact, folded structure.
J Mol Graph 1992 Mar
PMID:Molecular conformation of ubiquitinated structures and the implications for regulatory function. 132 99

The role of protein synthesis in the control of phosphoenolpyruvate carboxykinase (PEPCK; 4.1.1.32) mRNA turnover was studied in FTO-2B rat hepatoma cells. A previous study demonstrated that incubation of these cells with cAMP prolongs the half-life of the otherwise short-lived PEPCK mRNA. The decay rate of PEPCK mRNA was also slowed in cells incubated with cycloheximide, but not in cells incubated with other translation inhibitors, such as puromycin or pactamycin, even though protein synthesis was inhibited 85-95% by these agents. No correlation was noted between the rate of L-[3H]valine incorporation into cellular proteins and PEPCK mRNA half-life, suggesting that protein synthesis per se is not required for breakdown of the mRNA. Exposure of cells to the translation initiation inhibitor pactamycin together with cycloheximide abolished the "slowing" effect of cycloheximide, and PEPCK mRNA decayed at the same rate as in cells incubated in the presence of pactamycin alone. In contrast, pactamycin did not reverse the effect of cAMP, and the mRNA decayed at the same slow rate in cells incubated in the presence of either (Bu)2cAMP alone or (Bu)2cAMP together with pactamycin. Since pactamycin promotes polysomes dissociation, these results suggest that cAMP enhances the stability of a polysome-free PEPCK mRNA. Furthermore, these results strongly indicate that neither the rapid decay of PEPCK mRNA nor the cAMP-mediated stabilization of the mRNA requires on-going protein synthesis.
Mol Endocrinol 1992 Sep
PMID:The role of protein synthesis in the decay of phosphoenolpyruvate carboxykinase messenger RNA. 133 75


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