Peptidase M56-like, integral membrane metallopeptidase in bacteria
This family contains peptidase M56, which includes zinc metalloprotease domain in MecR1 as well as BlaR1. MecR1 is a transmembrane beta-lactam sensor/signal transducer protein that regulates the expression of an altered penicillin-binding protein PBP2a, which resists inactivation by beta-lactam antibiotics, in methicillin-resistant Staphylococcus aureus (MRSA). BlaR1 regulates the inducible expression of a class A beta-lactamase that hydrolytically destroys certain beta-lactam antibiotics in MRSA. Both, MecR1 and BlaR1, are transmembrane proteins that consist of four transmembrane helices, a cytoplasmic zinc protease domain, and the soluble C-terminal extracellular sensor domain, and are highly similar in sequence and function. The signal for protein expression is transmitted by site-specific proteolytic cleavage of both the transducer, which auto-activates, and the repressor, which is inactivated, unblocking gene transcription. All members contain the zinc metalloprotease motif (HEXXH). Homologs of this peptidase domain are also found in a number of other bacterial genome sequences, most of which are as yet uncharacterized.