Fate of the coactivator in the induction of BlaP β-lactamase in Bacillus licheniformis 749/I

In bacteria, the production of a β-lactamase, an hydrolase specific to β-lactam antibiotics, may be constitutive or inducible. In Bacillus licheniformis 749/I the presence of a β-lactam in the external media is detected by a protein relay producing an intracellular signal which leads to the induction of BlaP β-lactamase expression. The blaP gene is included in a divergeon along with blaI, coding for a cytoplasmic repressor, and blaR1, coding for a penicillin membrane receptor. Both, the acylation of the extracellular domain of BlaR1 by a β-lactam together with cellular stress due to the presence of the antibiotic outside the cell generate a dipeptide (coactivator) resulting from the peptidoglycan turnover that destabilizes BlaI repressor-DNA complex, leading to the expression of β-lactam resistance.