Peptidase M48C Ste24p bepA-like, integral membrane protein
This family contains peptidase M48C Ste24p protease bepA (formerly yfgC)-like proteins considered to be putative metallopeptidases, containing a zinc-binding motif, HEXXH, and a COOH-terminal ER retrieval signal (KKXX). They proteolytically remove the C-terminal three residues of farnesylated proteins. They are integral membrane proteins associated with the endoplasmic reticulum and golgi, binding one zinc ion per subunit. In eukaryotes, Ste24p is required for the first NH2-terminal proteolytic processing event within the a-factor precursor, which takes place after COOH-terminal CAAX modification (C is cysteine; A is usually aliphatic; X is one of several amino acids) is complete. Mutation studies have shown that the HEXXH protease motif, which is extracellular but adjacent to a transmembrane domain and therefore close to the membrane surface, is critical for Ste24p activity. Several members of this family also contain tetratricopeptide (TPR) repeat motifs, which are involved in a variety of functions including protein-protein interactions. BepA has been shown to possess protease activity and is responsible for the degradation of incorrectly folded LptD, an essential outer-membrane protein (OMP) involved in OM transport and assembly of lipopolysaccharide. Overexpression of the bepA protease causes abnormal biofilm architecture.
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