Ste24 metalloendopeptidases belong to MEROPS family M48 and contain peptidases related to S. cerevisiae Ste24. They are integral membrane proteins with seven transmembrane domains, residing in the membrane of the endoplasmic reticulum, with the N-terminus in the lumen and the active site and the C-terminus in the cytoplasm. They are prenyl proteases (family I), having a requirement for substrates that are prenylated at a C-terminal motif known as CAAX, in which A is an aliphatic residue, and the lipid is attached to the cysteine residue. (Note that peptidases in family M79, prenyl-protease family II, catalyse a similar reaction to those in family M48 - the specificities are overlapping but are not identical.) (Adapted from FBrf0239469 and FBrf0218548.)