1cxh
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COMPLEX OF CGTASE WITH MALTOTETRAOSE AT ROOM TEMPERATURE AND PH 9.6 BASED ON DIFFRACTION DATA OF A CRYSTAL SOAKED WITH MALTOHEPTAOSE
OverviewOverview
Asp-229, Glu-257, and Asp-328 constitute the catalytic residues in, cyclodextrin glycosyl transferase from Bacillus circulans strain 251. Via, site-directed mutagenesis constructed D229N, E257Q, and D328N mutant, proteins showed a 4,000-60,000-fold reduction of cyclization activity. A, D229N/E257Q double mutant showed a 700,000-fold reduction and was, crystallized for use in soaking experiments with alpha-cyclodextrin., Crystal structures were determined of wild type CGTase soaked at elevated, pH with alpha-cyclodextrin (resolution, 2.1 A) and maltoheptaose (2.4 A)., In addition, structures at cryogenic temperature were solved of the, unliganded enzyme (2.2 A) and of the D229N/E257Q mutant after soaking with, alpha-cyclodextrin (2.6 A). In the crystals soaked in alpha-cyclodextrin, and maltoheptaose, a maltotetraose molecule is observed to bind in the, active site. Residue 229 is at hydrogen bonding distance from the C-6, hydroxyl group of the sugar, which after cleavage will contain the new, reducing end. In the D229N/E257Q double mutant structure, two, alpha-cyclodextrins are observed to replace two maltoses at the E-domain, thus providing structural information on product inhibition via binding to, the enzyme's raw starch binding domain.
About this StructureAbout this Structure
1CXH is a Single protein structure of sequence from Bacillus circulans with MAL and CA as ligands. Active as Cyclomaltodextrin glucanotransferase, with EC number 2.4.1.19 Full crystallographic information is available from OCA.
ReferenceReference
Crystallographic studies of the interaction of cyclodextrin glycosyltransferase from Bacillus circulans strain 251 with natural substrates and products., Knegtel RM, Strokopytov B, Penninga D, Faber OG, Rozeboom HJ, Kalk KH, Dijkhuizen L, Dijkstra BW, J Biol Chem. 1995 Dec 8;270(49):29256-64. PMID:7493956
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