A probable intramembrane site-2 protease (S2P) that cleaves type-2 transmembrane proteins within their membrane-spanning domains. Cleaves PbpB (PBP3, FtsI) near 'Ala-102' and 'Ala-103' in response to oxidative stress; cleavage is inhibited by Wag31-PbpB interaction. Probably also cleaves anti-sigma factors RskA, RslA and RsmA but not RsdA. Regulated intramembrane proteolysis (RIP) occurs when an extracytoplasmic signal (possibly oxidative stress) triggers a concerted proteolytic cascade to transmit information and elicit cellular responses. The membrane-spanning regulatory substrate protein (includes anti-sigma factors RskA, RslA, RsmA, and PbpB in M.tuberculosis) is first cut extracytoplasmically (site-1 protease, S1P), then within the membrane itself (site-2 protease, S2P, this entry), while cytoplasmic proteases finish degrading the regulatory protein, liberating the effector protein (ECF sigma factors SigK, SigL and SigM). Inhibited by metal chelator o-phenanthroline. Was identified as a high-confidence drug target. Belongs to the peptidase M50B family.