REGULATION OF THE BETA-LACTAMASE BLAL OF STREPTOMYCES-CACAOI - THE PRODUCT OF THE BLAB REGULATORY GENE IS AN INTERNAL MEMBRANE-BOUND PROTEIN

The beta-lactamase-encoding gene blaL, cloned from Streptomyces cacaoi in Streptomyces lividans, is inducible by beta-lactam compounds. This regulation has been shown to depend on the products of two open readi ng frames, ORF1 (blaA) and ORF2 (blaB) [Lenzini, Magdalena, Fraipont, Joris, Matagne and Dusart (1992) Mol. Gen. Genet. 235, 41-48]. BlaA be longs to the LysR family of transcription activators, whereas BlaB sha res some features with the penicillin-recognizing proteins. BlaB has n ow been overexpressed in Escherichia coli, purified and used for antib ody preparation. Immunoblotting of cell-fractionated materials from S. cacaoi showed that BlaB is attached to the internal face of the cytop lasmic membrane. It could not be released by high salt concentrations or EDTA, but only by protease treatment. Under the assay conditions, B laB did not act as a penicillin-binding protein, a beta-lactamase, a D -amino-peptidase or a target in a phosphorylation step.