The araIc mutation in Escherichia coli B/r

The araIc allele is a cis-acting mutation which has been used to define the araBAD promoter in Escherichia coli B/r. Nineteen araIc mutants were originally isolated by Englesberg and co-workers as Ara+ "revertants" of an araC deletion mutant (Englesberg et al. J. Mol. Biol. 43:281-298, 1969). The mutants constitutively expressed araBAD gene products in the absence of functional araC activator protein. Eight of the araIc mutations have been cloned by in vivo recombination onto pBR322-ara hybrid plasmids. Restriction and DNA sequence analysis of these araIc mutations showed that they result from a single base-pair change located at -35 in the araBAD promoter.