title: Structure and mechanism of a proline-specific aminopeptidase from Escherichia coli.
abstract: The structure of the proline-specific aminopeptidase (EC 3.4.11.9) from Escherichia coli has been solved and refined for crystals of the native enzyme at a 2.0-A resolution, for a dipeptide-inhibited complex at 2.3-A resolution, and for a low-pH inactive form at 2.7-A resolution. The protein crystallizes as a tetramer, more correctly a dimer of dimers, at both high and low pH, consistent with observations from analytical ultracentrifuge studies that show that the protein is a tetramer under physiological conditions. The monomer folds into two domains. The active site, in the larger C-terminal domain, contains a dinuclear manganese center in which a bridging water molecule or hydroxide ion appears poised to act as the nucleophile in the attack on the scissile peptide bond of Xaa-Pro. The metal-binding residues are located in a single subunit, but the residues surrounding the active site are contributed by three subunits. The fold of the protein resembles that of creatine amidinohydrolase (creatinase, not a metalloenzyme). The C-terminal catalytic domain is also similar to the single-domain enzyme methionine aminopeptidase that has a dinuclear cobalt center.
authors.affiliation: Department of Biochemistry, University of Sydney, New South Wales 2006, Australia.
authors.forename: M C
authors.initials: MC
authors.lastname: Wilce
authors.forename: C S
authors.initials: CS
authors.lastname: Bond
authors.forename: N E
authors.initials: NE
authors.lastname: Dixon
authors.forename: H C
authors.initials: HC
authors.lastname: Freeman
authors.forename: J M
authors.initials: JM
authors.lastname: Guss
authors.forename: P E
authors.initials: PE
authors.lastname: Lilley
authors.forename: J A
authors.initials: JA
authors.lastname: Wilce
mesh_terms: D000626:Aminopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D004926:Escherichia coli / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D000626:Aminopeptidases; C022750:X-Pro aminopeptidase