1kxh
From Proteopedia
Crystal structure of the complex between an inactive mutant of psychrophilic alpha-amylase (D174N) and acarbose
Overview
The psychrophilic Pseudoalteromonas haloplanctis alpha-amylase is shown to form ternary complexes with two alpha-amylase inhibitors present in the active site region, namely, a molecule of Tris and a trisaccharide inhibitor or heptasaccharide inhibitor, respectively. The crystal structures of these complexes have been determined by X-ray crystallography to 1.80 and 1.74 A resolution, respectively. In both cases, the prebound inhibitor Tris is expelled from the active site by the incoming oligosaccharide inhibitor substrate analogue, but stays linked to it, forming well-defined ternary complexes with the enzyme. These results illustrate competition in the crystalline state between two inhibitors, an oligosaccharide substrate analogue and a Tris molecule, bound at the same time in the active site region. Taken together, these structures show that the enzyme performs transglycosylation in the complex with the pseudotetrasaccharide acarbose (confirmed by a mutant structure), leading to a well-defined heptasaccharide, considered as a more potent inhibitor. Furthermore, the substrate-induced ordering of water molecules within a channel highlights a possible pathway used for hydrolysis of starch and related poly- and oligosaccharides.
About this Structure
1KXH is a Single protein structure of sequence from Pseudoalteromonas haloplanktis. Full crystallographic information is available from OCA.
Reference
Crystallographic evidence of a transglycosylation reaction: ternary complexes of a psychrophilic alpha-amylase., Aghajari N, Roth M, Haser R, Biochemistry. 2002 Apr 2;41(13):4273-80. PMID:11914073 Page seeded by OCA on Fri May 2 23:17:31 2008
