1cgu
From Proteopedia
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CATALYTIC CENTER OF CYCLODEXTRIN GLYCOSYLTRANSFERASE DERIVED FROM X-RAY STRUCTURE ANALYSIS COMBINED WITH SITE-DIRECTED MUTAGENESIS
Overview
An X-ray structure analysis of a crystal of mutant Asp229----Ala of, cyclodextrin glycosyltransferase from Bacillus circulans (Ec 2.4.1.19), that had been shortly exposed to beta-cyclodextrin showed density, corresponding to a maltose bound at the catalytic center. The crystal, structure was refined to an R-factor of 18.7% at 2.5-A resolution. The, catalytic center is defined by homology with the structurally known, alpha-amylases and by the observation that mutants Asp229----Ala and, Asp328----Ala are almost inactive. By model building, the density-defined, maltose was extended to a full beta-cyclodextrin, which then indicated the, general locations of seven subsites for glucosyl units. The catalytically, competent residues Asp229, Glu257, and Asp328 are at the reducing end of, the density-defined maltose. In the unligated wild-type structure, Glu257, and Asp328 form a 2.6-A hydrogen bond between their carboxylates in an, arrangement that resembles those of the catalytically competent, carboxylates in acid proteases. Presumably, the first catalytic step is an, attack of the proton between Glu257 and Asp328 on the oxygen of the, glycosidic bond.
About this Structure
1CGU is a Single protein structure of sequence from Bacillus circulans with CA as ligand. Active as Cyclomaltodextrin glucanotransferase, with EC number 2.4.1.19 Full crystallographic information is available from OCA.
Reference
Catalytic center of cyclodextrin glycosyltransferase derived from X-ray structure analysis combined with site-directed mutagenesis., Klein C, Hollender J, Bender H, Schulz GE, Biochemistry. 1992 Sep 22;31(37):8740-6. PMID:1390660
Page seeded by OCA on Tue Nov 20 12:26:18 2007
