Domain

Peptidase M17, leucyl aminopeptidase, C-terminal (IPR000819)

Short name: Peptidase_M17_C

Domain relationships

None.

Description

Over 70 metallopeptidase families have been identified to date. In these enzymes a divalent cation which is 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. 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 the MEROPS peptidase family M17 (leucyl aminopeptidase family, clan MF), the type example being leucyl aminopeptidase from Bos taurus (Bovine).

Aminopeptidases are exopeptidases involved in the processing and regular turnover of intracellular proteins, although their precise role in cellular metabolism is unclear [PMID: 1555602, PMID: 2395881]. Leucine aminopeptidases cleave leucine residues from the N-terminal of polypeptide chains, but substantial rates are evident for all amino acids [PMID: 2395881].

The enzymes exist as homo-hexamers, comprising 2 trimers stacked on top of one another [PMID: 2395881]. Each monomer binds 2 zinc ions and folds into 2 alpha/beta-type quasi-spherical globular domains, producing a comma-like shape [PMID: 2395881]. The N-terminal 150 residues form a 5-stranded beta-sheet with 4 parallel and 1 anti-parallel strand sandwiched between 4 alpha-helices [PMID: 2395881]. An alpha-helix extends into the C-terminal domain, which comprises a central 8-stranded saddle-shaped beta-sheet sandwiched between groups of helices, forming the monomer hydrophobic core [PMID: 2395881]. A 3-stranded beta-sheet resides on the surface of the monomer, where it interacts with other members of the hexamer [PMID: 2395881]. The 2 zinc ions and the active site are entirely located in the C-terminal catalytic domain [PMID: 2395881].

GO terms

Biological Process

GO:0006508 proteolysis

Molecular Function

GO:0004177 aminopeptidase activity

Cellular Component

GO:0005622 intracellular

Contributing signatures

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