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 reading frames, ORF1 (blaA) and
ORF2 (blaB) [Lenzini, Magdalena, Fraipont, Joris, Matagne and Dusart (1992) Mol.
Gen. Genet. 235, 41-48]. BlaA belongs to the LysR family of transcription
activators, whereas BlaB shares some features with the penicillin-recognizing
proteins. BlaB has now been overexpressed in Escherichia coli, purified and used
for antibody preparation. Immunoblotting of cell-fractionated materials from S.
cacaoi showed that BlaB is attached to the internal face of the cytoplasmic
membrane. It could not be released by high salt concentrations or EDTA, but only
by protease treatment. Under the assay conditions, BlaB did not act as a
penicillin-binding protein, a beta-lactamase, a D-amino-peptidase or a target in
a phosphorylation step.