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. 1976 Apr;126(1):56–63. doi: 10.1128/jb.126.1.56-63.1976

Threonine deaminase from Escherichia coli: feedback-hypersensitive enzyme from a genetic regulatory mutant.

D H Calhoun
PMCID: PMC233259  PMID: 770442

Abstract

A mutation, ilvA538, in the gene coding for the biosynthetic L-threonine deaminase of Escherichia coli K-12 has previously been demonstrated to have pleiotropic regulatory effects leading to low and invariant expression of some of the isoleucine-valine biosynthetic enzyme, and altered expression of the branched-chain aminoacyl-tRNA synthetases. Strain PS187, which carries the ilvA538 allele, has a partial growth requirement for L-isoleucine and is characterized by a sensitivity to growth inhibition by L-leucine. The experiments reported here demonstrate that the L-threonine deaminase produced by strain PS187 is hypersensitive to inhibition by the pathway end product L-isoleucine. In addition, L-leucine, which acts at relatively high concentrations in vitro as an inhibitor of L-threonine deaminase from the wild type, is a more potent inhibitor of the activity of the mutant enzyme. Forty-six derivatives of strain PS187 were isolated as spontaneous mutants resistant to the growth-inhibitory effects of L-leucine. Two of these, strains MSR14 and MSR16, produce an L-threonine deaminase that is more resistant than the wild type to L-isoleucine inhibition, and intermediate between the wild type and strain PS187 with respect to L-leucine inhibition. Strains MSR14 and MSR16 produce L-threonine deaminase and dihydroxyacid dehydrase, the ilvD gene product, at the low levels characteristic of the parent strain. Other L-leucine-resistant derivatives of strain PS187 produce higher levels of the feedback-hypersensitive L-threonine deaminase. Thus, the sensitivity to growth inhibition by L-leucine observed with strain PS187 appears to be related both to the hypersensitivity of L-threonine deaminase to inhibition of catalytic activity and to the low level of ilv gene expression. The results reported here indicated that L-threonine deaminase is structurally altered in strain PS187, and thus provide further support for the proposal that L-threonine deaminase participates as a genetic regulatory element for the expression of the branched-chain amino acid biosynthetic enzymes.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Calhoun D. H. Autoregulation of gene expression. Annu Rev Microbiol. 1975;29:275–299. doi: 10.1146/annurev.mi.29.100175.001423. [DOI] [PubMed] [Google Scholar]
  2. Calhoun D. H., Hatfield G. W. Autoregulation: a role for a biosynthetic enzyme in the control of gene expression. Proc Natl Acad Sci U S A. 1973 Oct;70(10):2757–2761. doi: 10.1073/pnas.70.10.2757. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Calhoun D. H., Jensen R. A. Significance of altered carbon flow in aromatic amino acid synthesis: an approach to the isolation of regulatory mutants in Pseudomonas aeruginosa. J Bacteriol. 1972 Jan;109(1):365–372. doi: 10.1128/jb.109.1.365-372.1972. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Calhoun D. H., Kuska J. S., Hatfield G. W. Threonine deaminase from Escherichia coli. II. Maturation and physical properties of the enzyme from a mutant altered in its regulation of gene expression. J Biol Chem. 1975 Jan 10;250(1):127–131. [PubMed] [Google Scholar]
  5. Calhoun D. H., Rimerman R. A., Hatfield G. W. Threonine deaminase from Escherichia coli. I. Purification and properties. J Biol Chem. 1973 May 25;248(10):3511–3516. [PubMed] [Google Scholar]
  6. Cortese R., Landsberg R., Haar R. A., Umbarger H. E., Ames B. N. Pleiotropy of hisT mutants blocked in pseudouridine synthesis in tRNA: leucine and isoleucine-valine operons. Proc Natl Acad Sci U S A. 1974 May;71(5):1857–1861. doi: 10.1073/pnas.71.5.1857. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. DAVIS B. D., MINGIOLI E. S. Mutants of Escherichia coli requiring methionine or vitamin B12. J Bacteriol. 1950 Jul;60(1):17–28. doi: 10.1128/jb.60.1.17-28.1950. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Goldberger R. F. Autogenous regulation of gene expression. Science. 1974 Mar 1;183(4127):810–816. doi: 10.1126/science.183.4127.810. [DOI] [PubMed] [Google Scholar]
  9. Hatfield G. W., Burns R. O. Specific binding of leucyl transfer RNA to an immature form of L-threonine deaminase: its implications in repression. Proc Natl Acad Sci U S A. 1970 Aug;66(4):1027–1035. doi: 10.1073/pnas.66.4.1027. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Jackson J., Williams L. S., Umbarger H. E. Regulation of synthesis of the branched-chain amino acids and cognate aminoacyl-transfer ribonucleic acid synthetases of Escherichia coli: a common regulatory element. J Bacteriol. 1974 Dec;120(3):1380–1386. doi: 10.1128/jb.120.3.1380-1386.1974. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Kovach J. S., Phang J. M., Ference M., Goldberger R. F. Studies on repression of the histidine operon. II. The role of the first enzyme in control of the histidine system. Proc Natl Acad Sci U S A. 1969 Jun;63(2):481–488. doi: 10.1073/pnas.63.2.481. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Levinthal M., Williams L. S., Umbarger H. E. Role of threonine deaminase in the regulation of isoleucine and valine biosynthesis. Nat New Biol. 1973 Nov 21;246(151):65–68. doi: 10.1038/newbio246065a0. [DOI] [PubMed] [Google Scholar]
  13. Pledger W. J., Umbarger H. E. Isoleucine and valine metabolism in Escherichia coli. XXII. A pleiotropic mutation affecting induction of isomeroreductase activity. J Bacteriol. 1973 Apr;114(1):195–207. doi: 10.1128/jb.114.1.195-207.1973. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Rizzino A. A., Bresalier R. S., Freundlich M. Derepressed levels of the isoleucine-valine and leucine enzymes in his T 1504, a strain of Salmonella typhimurium with altered leucine transfer ribonucleic acid. J Bacteriol. 1974 Feb;117(2):449–455. doi: 10.1128/jb.117.2.449-455.1974. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Rogerson A. C., Freundlich M. Control of isoleucine, valine and leucine biosynthesis. 8. Mechanism of growth inhibition by leucine in relaxed and stringent strains of Escherichia coli K-12. Biochim Biophys Acta. 1970 Apr 14;208(1):87–98. doi: 10.1016/0304-4165(70)90051-6. [DOI] [PubMed] [Google Scholar]
  16. Vonder Haar R. A., Umbarger H. E. Isoleucine and valine metabolism in Escherichia coli. XIX. Inhibition of isoleucine biosynthesis by glycyl-leucine. J Bacteriol. 1972 Oct;112(1):142–147. doi: 10.1128/jb.112.1.142-147.1972. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Wasmuth J. J., Umbarger H. E. Role for free isoleucine of glycyl-leucine in the repression of threonine deaminase in Escherichia coli. J Bacteriol. 1974 Jan;117(1):29–39. doi: 10.1128/jb.117.1.29-39.1974. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Wasmuth J., Umbarger H. E., Dempsey W. B. A role for a pyridoxne derivative in the multivalent repression of the isoleucine and valine biosynthetic enzymes. Biochem Biophys Res Commun. 1973 Mar 5;51(1):158–164. doi: 10.1016/0006-291x(73)90522-6. [DOI] [PubMed] [Google Scholar]

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