SEQUENCING ANALYSIS OF MUTATION POINTS IN THE BIOTIN OPERON OF BIOTIN-OVERPRODUCING ESCHERICHIA-COLI MUTANTS

We analyzed mutation points of the biotin operon from biotin-overprodu cing mutants of Escherichia coli resistant to two biotin analogs, acti thiazic acid and 5-(2-thienyl)-valeric acid, by DNA sequencing. The bi otin operons cloned from these mutants were classified into three grou ps. One point mutation, which was a GC --> AT change within the operat or overlapping the - 10 region of the rightward (bioB) promoter, was c onsidered to result in disruption of operator structure and enhancemen t of promoter activity. Two other point mutations, which were both GC --> AT changes just before and after the initiation codon of the bioB gene, were considered to activate the translation efficiency. These mu tations significantly accelerated the biotin-forming activity from det hiobiotin in cell-free extracts.