Absence of acetohydroxy acid synthase III in Salmonella typhimurium is due to early termination of translation within the ilvl gene.
The cryptic ilvlH locus of Salmonella typhimurium has genetic information for two distinct subunits of acetohydroxy acid synthase III. We show that the ilvH-encoded subunit is normally translated and the lack of activity is due to early termination of translation within the promoter-proximal ilvl gene. Analysis of the 5' region of the operon led to identification of the promoter and the amino-terminal part of ilvl. Expression of this gene in a mutant producing acetohydroxy acid synthase is due to a transversion which creates a UUA (leucine) codon in the place of a UGA (stop) codon present in position 12 of the wild-type coding region.
International Institute of Genetics and Biophysics, CNR, Naples, Italy.
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D000095:Acetolactate Synthase / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D005798:Genes, Bacterial; D007527:Isoenzymes / Q000235:genetics; D008969:Molecular Sequence Data; D010443:Peptide Chain Termination, Translational; D012045:Regulatory Sequences, Nucleic Acid; D012486:Salmonella typhimurium / Q000235:genetics* / Q000254:growth & development
D007527:Isoenzymes; D000095:Acetolactate Synthase