PMID:2188950
| Citation |
Alexander-Caudle, C, Latinwo, LM and Jackson, JH (1990) Acetohydroxy acid synthase activity from a mutation at ilvF in Escherichia coli K-12. J. Bacteriol. 172:3060-5 |
|---|---|
| Abstract |
Examination of the ilvF locus at 54 min on the Escherichia coli K-12 chromosome revealed that it is a cryptic gene for expression of a valine-resistant acetohydroxy acid synthase (acetolactate synthase; EC 4.1.3.18) distinct from previously reported isozymes. A spontaneous mutation, ilvF663, yielded IlvF+ enzyme activity that was multivalently repressed by all three branched-chain amino acids, was completely insensitive to feedback inhibition, was highly stable at elevated temperatures, and expressed optimal activity at 50 degrees C. The IlvF+ enzyme activity was expressed in strains in which isozyme II was inactive because of the ilvG frameshift in the wild-type strain K-12 and isozymes I and III were inactivated by point mutations or deletions. Tn5 insertional mutagenesis yielded two IlvF- mutants, with the insertion in ilvF663 in each case. These observations suggest that the ilvF663 locus may be a coding region for a unique acetohydroxy acid synthase activity. |
| Links | |
| Keywords |
Acetolactate Synthase/analysis; Acetolactate Synthase/genetics; Chromosome Mapping; Escherichia coli/enzymology; Escherichia coli/genetics; Gene Expression Regulation, Bacterial; Genes, Bacterial; Hot Temperature; Hydrogen-Ion Concentration; Isoleucine/biosynthesis; Isoleucine/genetics; Molecular Weight; Mutation; Oxo-Acid-Lyases/analysis; Valine/biosynthesis; Valine/genetics |
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