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)

Kinetic studies have been performed on the "family" of aminoacyl synthetases from calf liver. All assays were based on the esterification of amino acids to tRNA. Optimized reaction conditions for each synthetase are reported. Most of the synthetases show hyperbolic kinetics with respect to both amino acid and tRNA concentration, however a few show sigmoidal kinetics with respect to one substrate. Arginine, methionine and proline synthetases show sigmoidal kinetics with respect to mixed tRNA solutions and have Hill coefficients of 1.30, 1.10 and 1.20 respectively. Alanine and isoleucine synthetases show sigmoidal kinetics with respect to amino acid concentration and have Hill coefficients of 1.21 and 1.40 respectively.
Mol Cell Biochem 1977 Aug 19
PMID:Aminoacyl-tRNA synthetases from calf liver: optimized assay conditions and kinetic properties. 2 May 69

Mutants of an aminopterin-resistant strain of pneumococcus possessing four different suppressor genes have been isolated after mutagenesis with 5-BUdR. The suppressed strains exhibit a partial revertant phenotype since the parental aminopterin resistance remained unchanged but the associated sensitivity to an excess concentration of the branched chain amino acids L-isoleucine, L-valine and L-leucine was diminished almost to the level of the wild-type strain C13. The suppressor mutations had therefore dissociated the two properties associated with a mutation in the amiA cistron, namely aminopterin resistance and isoleucine sensitivity. The suppressor genes reduced the sensitivity to isoleucine of a number of amiA mutants, but had no effect on the level of resistance to a number of unrelated genes conferring resistance to other antibacterial substances. The suppressor mutations themselves did not confer resistance to aminopterin. Mapping of the suppressor mutations by recombination analysis and by clonal analysis showed them to be intragenic lying in the region near to the amiA-r19, amiA-r23, amiA-r17 loci.
Mol Gen Genet 1979 Jul 24
PMID:Suppressor mutations causing partial reversion in the amiA region of Pneumococcus. 3 21

The promoter of the threonine operon was joined to the structural genes of the lac operon in Escherichia coli K 12. The synthesis of beta-galactosidase was thus repressed by threonine plus isoleucine in the fusion strains. To isolate mutations which affect the expression of the threonine operon, alterations in the level of expression of the lacZ gene were selected. A new type of regulatory mutation was discovered.
Mol Gen Genet 1978 Jun 01
PMID:New regulatory mutations affecting the expression of the threonine operon in Escherichia coli K-12. 9 15

Ribosomal protein S5 was isolated from wild type Bacillus subtilis ATCC 6633 and from a spectinomycin resistant mutant (BSPC 111) derived from spectinomycin sensitive to resistance is accomtrypsin and all the tryptic peptides were isolated by column- and paper-chromatography. By comparative amino acid analyses of the peptides, it was demonstrated that the S5 from the mutant differs from the wild type S5 by a replacement of one amino acid, namely lysine by isoleucine in the peptide T9. The results are compared with E. coli spectinomycin resistant mutants.
Mol Gen Genet 1976 Feb 27
PMID:Amino acid replacement in the protein S5 from a spectinomycin resistant mutant of Bacillus subtilis. 13 Dec 41

1. The metabolic responses to an oral glucose tolerance test (100 g) and an intravenous insulin provocation test (0-1 i.u./kg) were studied in nine control subjects and nine patients with Huntington's chorea. 2. Plasma glucose responses to these stimuli were identical in both groups. 3. High fasting concentrations of non-esterified fatty acid (NEFA) were recorded in the choreic patients when compared with control subjects. This difference was maintained under hypoglycaemic conditions. However, during hyperglycaemia the differences in NEFA concentrations between the groups was abolished. 4. Total plasma tryptophan concentrations were equal in the two groups. Free plasma tryptophan, however, was markedly reduced in the choreic group, and this appeared to be a result of a disturbed relationship between free tryptophan and NEFA concentrations. The abnormalities in free tryptophan values were sensitive to plasma glucose concentrations, as hyperglycaemic conditions markedly reduced the differences between the choreic and control group. 5. Patients with Huntington's chorea showed reduced fasting plasma concentrations of leucine, isoleucine and valine.
Clin Sci Mol Med 1977 Mar
PMID:Plasma glucose, non-esterified fatty acids and amino acids in Huntington's chorea. 13 25

With puromycin one can recognize when the synthesis of a given protein is dependent on amino acyl tRNA that is present in rate limiting amount. We demonstrate this use of puromycin by its interaction with another inhibitor, L-o-methylthreonine. L-o-methylthreonine lowers the Ile-tRNA concentration in the cell, thereby inhibiting synthesis of proteins containing isoleucine. In certain rabbits, the alpha hemoglobin chain has three isoleucyl residues and the beta chain none. L-o-methylthreonine thus inhibits alpha globin synthesis in intact reticulocytes from these rabbits. When puromycin and L-o-methylthreonine are used together, the two inhibitors synergize in inhibiting alpha globin synthesis. Hence, puromycin is a more effective inhibitor when the Ile-tRNA concentration is lowered. Cycloheximide and sodium fluoride have different modes of action from puromycin. Neither synergizes with L-o-methylthreonine; instead, the interaction is less than additive. We have found that beta chain synthesis in rabbit reticulocytes is more sensitive than alpha to inhibition by puromycin. This difference could reflect either differences in amino acid sequence or tRNA dependent limitations of beta chain elongation. The switch from fetal to adult hemoglobin in humans does not involve changes in limiting amino acyl tRNA because, for cord blood from infants of different developmental ages, the puromycin sensitivity of incorporation into gamma and beta chains remains constant.
Mol Cell Biochem 1978 Feb 24
PMID:Testing with puromycin and amino acyl tRNAs that limit the rate of peptide chain extension. 24 96

A hybridization assay using Escherichia coli K-12 DNA isolated from the specialized transducing bacteriophage gammaCI857St68h80 dilv was used to examine the rate of synthesis of the messenger RNA's (mRNA) derived from the isoleucine-valine (ilv) gene cluster of Salmonella typhimurium. In all cases examined, changes in ilv enzyme levels could be correlated with changes in the rate of synthesis of ilv mRNA. Several well characterized regulatory mutants of S. typhimurium had rates of synthesis of ilv mRNA 3 to 8-fold higher than the repressed wild-type strain. The increased rates of ilv mRNA synthesis found in a hisT strain as well as in isoleucyl-and leucyl-tRNA SYNTHETASE MUTANTS, STRONGLY SUGGESTS A ROLE FOR BRANCHED-CHAIN AMINOACYL-TRNA's in transcriptional control.
Mol Gen Genet 1977 Mar 07
PMID:Detection of messenger RNA from the isoleucine--valine operons of Salmonella typhimurium by heterologous DNA-RNA hybridization: involvement of transfer RNA in transcriptional repression. 32 61

We studied the production of the ilvG gene product, the valine resistant acetolactate synthase isoenzyme II, in an ilvO+ G+ ilvB ilvHI derivative of Escherichia coli K-12. This strain contains mutations in the structural genes for the valine sensitive acetolactate synthase isoenzymes I and III. We find that the ilvG gene is not expressed in this strain when gworn with either isoleucine and valine or with isoleucine, leucine and valine, or when limited for either isoleucine or valine. Since we previously found that the ilvG gene is expressed in an ilvO603 containing strain (Favre et al., 1976), we presume that the mechanism by which E. coli K-12 regulates the ilv gene cluster is responsible for the lack of ilvG expression in the ilvO+ strain. The valine sensitivity of E. Coli K-12 is a consequence of this regulatory pattern.
Mol Gen Genet 1977 Nov 04
PMID:Growth inhibition of Escherichia coli K-12 by L-valine: a consequence of a regulatory pattern. 34 Aug 87

The use of triplet code words in E. coli, phiX174, MS2, and rabbit globin was examined. A significant deficiency of purines in the third position of four fold degenerate codons was noted, although its significance is not understood. There has been no consistent selection against uracil in pyrimidine restricted codons. For many amino acids the choice between code words appears random, while for arginine, isoleucine, and probably glycine, distinct biases exist which can be explained in terms of tRNA availability.
J Mol Evol 1978 Feb 21
PMID:Pattern and chance in the use of the genetic code. 34 96

We describe the regulatory properties of two strains carrying either the ilvA624 or the ilvA625 mutations, located in the structural gene for threonine deaminase. Crude extracts of both these strains possess a threonine deaminase activity migrating on polyacrylamide gels, differently from the wild type enzyme. Growth studies demonstrate that these mutations do not cause a limitation of isoleucine biosynthesis, suggesting normal catalytic activity of deaminase. A regulatory consequence of the ilvA624 allele is a derepression of the isoleucine-valine biosynthetic enzymes, which is recessive to an ilvA+ allele. The ilvA625 mutation causes a derepression which is dominant in an ilvA625/ILVA+ diploid. We interpret these data assuming that threonine deaminase, previously shown to be an autogenous regulator of the ilv genes, lacks a repressor function in the ilvA624 mutant, while in the ilvA625 mutant it is a better activator than wild type threonine deaminase. The data are discussed in terms of a model requiring that threonine deaminase, or a precursor of it, is in equilibrium between two forms, one being an activator of gene expression and the other being a repressor.
Mol Gen Genet 1978 Feb 07
PMID:Dual autogenous regulatory role of threonine deaminase in Escherichia coli K-12. 34 81


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