RseP-like Site-2 proteases (S2P), zinc metalloproteases (MEROPS family M50A), cleave transmembrane domains of substrate proteins, regulating intramembrane proteolysis (RIP) of diverse signal transduction mechanisms. In Escherichia coli, the S2P homolog RseP is involved in the sigmaE pathway of extracytoplasmic stress responses. Also included in this group are such homologs as Bacillus subtilis YluC, Mycobacterium tuberculosis Rv2869c S2P, and Bordetella bronchiseptica HurP. Rv2869c S2P appears to have a role in the regulation of prokaryotic lipid biosynthesis and membrane composition and YluC of Bacillus has a role in transducing membrane stress. This group includes bacterial and eukaryotic S2P/M50s homologs with either one or two PDZ domains present. PDZ domains are believed to have a regulatory role. The RseP PDZ domain is required for the inhibitory reaction that prevents cleavage of its substrate, RseA.