Repressor gene, blaI, for Bacillus licheniformis 749 β‐lactamase

The repressor gene, blaI, for the beta-lactamase of Bacillus licheniformis 749 was functional when cloned in Escherichia coli, but addition of a beta-lactam did not lead to induction. One plasmid contained fragments from the inducible strain (source of repressor), the other carried fragments from the blaI- mutant 749/C (target). blaI lies just 5' to the promoter for the structural gene, blaP, and the target is the promoter region between the two genes. Interaction with both promoters seemed necessary for full repression. BlaI is a hydrophilic protein (Mr 15036) with the some structural similarities to repressors from Gram-negative bacteria.