Peptidase M24, methionine aminopeptidase (IPR001714)

Short name: Pept_M24_MAP

Family relationships


Over 50 metallopeptidase families have been identified to date. In these enzymes, a divalent cation, usually zinc but may be cobalt, manganese or copper, activates the water molecule. The metal ion is held in place by amino acid ligands, usually three in number. In some families of co-catalytic metallopeptidases, two metal ions are observed in crystal structures ligated by five amino acids, with one amino acid ligating both metal ions. The known metal ligands are His, Glu, Asp or Lys and at least one other residue is required for catalysis, which may play an electrophillic role. Many metalloproteases contain an HEXXH motif, which has been shown in crystallographic studies to form part of the metal-binding site [PMID: 7674922]. The HEXXH motif is relatively common, but can be more stringently defined for metalloproteases as 'abXHEbbHbc', where 'a' is most often valine or threonine and forms part of the S1' subsite in thermolysin and neprilysin, 'b' is an uncharged residue, and 'c' a hydrophobic residue. Proline is never found in this site, possibly because it would break the helical structure adopted by this motif in metalloproteases [PMID: 7674922].

This group of metallopeptidases belong to MEROPS peptidase family M24 (clan MG), subfamilies M24A and M24B [PMID: 7674922].

Methionine aminopeptidase (EC: (MAP) is responsible for the removal of the amino-terminal (initiator) methionine from nascent eukaryotic cytosolic and cytoplasmic prokaryotic proteins if the penultimate amino acid is small and uncharged. All MAP studied to date are monomeric proteins that require cobalt ions for activity.

Two subfamilies of MAP enzymes are known to exist [PMID: 7644482, PMID: 8772380]. While being evolutionary related, they only share a limited amount of sequence similarity mostly clustered around the residues shown to be involved in cobalt-binding. The first family consists of enzymes from prokaryotes as well as eukaryotic MAP-1, while the second group is made up of archaeal MAP and eukaryotic MAP-2. The second subfamily also includes proteins which do not seem to be MAP, but that are clearly evolutionary related such as mouse proliferation-associated protein 1 and fission yeast curved DNA-binding protein.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.