1uh4
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Revision as of 02:00, 21 November 2007
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Thermoactinomyces vulgaris R-47 alpha-amylase 1/malto-tridecaose complex
Overview
The X-ray structures of complexes of Thermoactinomyces vulgaris R-47, alpha-amylase 1 (TVAI) with an inhibitor acarbose and an inactive mutant, TVAI with malto-hexaose and malto-tridecaose have been determined at 2.6, 2.0 and 1.8A resolution, and the structures have been refined to R-factors, of 0.185 (R(free)=0.225), 0.184 (0.217) and 0.164 (0.200), respectively, with good chemical geometries. Acarbose binds to the catalytic site of, TVAI, and interactions between acarbose and the enzyme are very similar to, those found in other structure-solved alpha-amylase/acarbose complexes, supporting the proposed catalytic mechanism. Based on the structure of the, TVAI/acarbose complex, the binding mode of pullulan containing alpha-(1,6), glucoside linkages could be deduced. Due to the structural difference, caused by the replaced amino acid residue (Gln396 for Glu) in the, catalytic site, malto-hexaose and malto-tridecaose partially bind to the, catalytic site, giving a mimic of the enzyme/product complex. Besides the, catalytic site, four sugar-binding sites on the molecular surface are, found in these X-ray structures. Two sugar-binding sites in domain N hold, the oligosaccharides with a regular helical structure of amylose, which, suggests that the domain N is a starch-binding domain acting as an anchor, to starch in the catalytic reaction of the enzyme. An assay of hydrolyzing, activity for the raw starches confirmed that TVAI can efficiently, hydrolyze raw starch.
About this Structure
1UH4 is a Single protein structure of sequence from Thermoactinomyces vulgaris with GLC, CA and MPD as ligands. Active as Alpha-amylase, with EC number 3.2.1.1 Full crystallographic information is available from OCA.
Reference
Complex structures of Thermoactinomyces vulgaris R-47 alpha-amylase 1 with malto-oligosaccharides demonstrate the role of domain N acting as a starch-binding domain., Abe A, Tonozuka T, Sakano Y, Kamitori S, J Mol Biol. 2004 Jan 16;335(3):811-22. PMID:14687576
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