1wl9
From Proteopedia
Structure of aminopeptidase P from E. coli
Overview
The effect of metal substitution on the activity and structure of the aminopeptidase P (APPro) from Escherichia coli has been investigated. Measurements of activity in the presence of Mn2+, Mg2+, Zn2+, Na+, and Ca2+ show that significant activity is seen only in the Mn-bound form of the enzyme. The addition of Zn2+ to [MnMn(APPro)] is strongly inhibitory. Crystal structures of [MnMn(APPro)], [MgMg(APPro)], [ZnZn(APPro)], [ZnMg(APPro)], [Ca_(APPro)], [Na_(APPro)], and [apo(APPro)] were determined. The structures of [Ca_(APPro)] and [Na_(APPro)] have a single metal atom at their active site. Surprisingly, when a tripeptide substrate (ValProLeu) was soaked into [Na_(APPro)] crystals in the presence of 200 mM Mg2+, the structure had substrate, but no metal, bound at the active site. The structure of apo APPro complexed with ValProLeu shows that the N-terminal amino group of a substrate can be bound at the active site by carboxylate side chains that normally bind the second metal atom, providing a model for substrate binding in a single-metal active enzyme. Structures of [MnMn(APPro)] and [ZnZn(APPro)] complexes of ProLeu, a product inhibitor, in the presence of excess Zn reveal a third metal-binding site, formed by two conserved His residues and the dipeptide inhibitor. A Zn atom bound at such a site would stabilize product binding and enhance inhibition.
About this Structure
1WL9 is a Single protein structure of sequence from Escherichia coli. This structure supersedes the now removed PDB entry 1az9. Full crystallographic information is available from OCA.
Reference
Structural and functional implications of metal ion selection in aminopeptidase P, a metalloprotease with a dinuclear metal center., Graham SC, Bond CS, Freeman HC, Guss JM, Biochemistry. 2005 Oct 25;44(42):13820-36. PMID:16229471 Page seeded by OCA on Sat May 3 13:50:01 2008
