Peptidase M14-like domain similar to rapid encystment phenotype 34 (REP34)
This family includes Francisella tularensis protein rapid encystment phenotype 34 (REP34) which is a zinc-containing monomeric protein demonstrating carboxypeptidase B-like activity. REP34 possesses a novel topology with its substrate binding pocket deviating from the canonical M14 peptidases with a possible catalytic role for a conserved tyrosine and distinct S1' recognition site. Thus, REP34, identified as an active carboxypeptidase and a potential key F. tularensis effector protein, may help elucidate a mechanistic understanding of F. tularensis infection of phagocytic cells. A functionally uncharacterized subgroup of the M14 family of metallocarboxypeptidases (MCPs). The M14 family are zinc-binding carboxypeptidases (CPs) which hydrolyze single, C-terminal amino acids from polypeptide chains, and have a recognition site for the free C-terminal carboxyl group, which is a key determinant of specificity. Two major subfamilies of the M14 family, defined based on sequence and structural homology, are the A/B and N/E subfamilies. Enzymes belonging to the A/B subfamily are normally synthesized as inactive precursors containing preceding signal peptide, followed by an N-terminal pro-region linked to the enzyme; these proenzymes are called procarboxypeptidases. The A/B enzymes can be further divided based on their substrate specificity; Carboxypeptidase A-like (CPA-like) enzymes favor hydrophobic residues while carboxypeptidase B-like (CPB-like) enzymes only cleave the basic residues lysine or arginine. The A forms have slightly different specificities, with Carboxypeptidase A1 (CPA1) preferring aliphatic and small aromatic residues, and CPA2 preferring the bulky aromatic side chains. Enzymes belonging to the N/E subfamily enzymes are not produced as inactive precursors and instead rely on their substrate specificity and subcellular compartmentalization to prevent inappropriate cleavages. They contain an extra C-terminal transthyretin-like domain, thought to be involved in folding or formation of oligomers. MCPs can also be classified based on their involvement in specific physiological processes; the pancreatic MCPs participate only in alimentary digestion and include carboxypeptidase A and B (A/B subfamily), while others, namely regulatory MCPs or the N/E subfamily, are involved in more selective reactions, mainly in non-digestive tissues and fluids, acting on blood coagulation/fibrinolysis, inflammation and local anaphylaxis, pro-hormone and neuropeptide processing, cellular response and others. Another MCP subfamily, is that of succinylglutamate desuccinylase /aspartoacylase, which hydrolyzes N-acetyl-L-aspartate (NAA), and deficiency in which is the established cause of Canavan disease. Another subfamily (referred to as subfamily C) includes an exceptional type of activity in the MCP family, that of dipeptidyl-peptidase activity of gamma-glutamyl-(L)-meso-diaminopimelate peptidase I which is involved in bacterial cell wall metabolism.
Comment:Metallocarboxypeptidases share the zinc binding motif HXXE...H, where the zinc ion is penta-coordinated to ND1 atoms of the histidines, OE1 and OE2 atoms of the glutamic acid, and to a water molecule in a slightly distorted tetrahedral manner.
Comment:In this structure, nickel is found in place of zinc, but has same interactions as zinc.
Structure:3B2Y: Shewanella denitrificans Os217 Metallopeptidase containing Ni in co-catalytic metalloactive site; contacts at 3.5A
Jiyao W et al.(2023). "The conserved domain database in 2023.",