Crystallographic studies of the interaction of cyclodextrin glycosyltransferase from Bacillus circulans strain 251 with natural substrates and products.
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 ...
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.
Related Citations:
X-Ray Structure of Cyclodextrin Glycosyltransferase Complexed with Acarbose. Implications for the Catalytic Mechanism of Glycosidases Strokopytov, B., Penninga, D., Rozeboom, H.J., Kalk, K.H., Dijkhuizen, L., Dijkstra, B.W. (1995) Biochemistry 34: 2234
Nucleotide Sequence and X-Ray Structure of Cyclodextrin Glycosyltransferase from Bacillus Circulans Strain 251 in a Maltose-Dependent Crystal Form Lawson, C.L.L., Van Montfort, R., Strokopytov, B., Rozeboom, H.J., Kalk, K.H., De Vries, G.E., Penninga, D., Dijkhuizen, L., Dijkstra, B.W. (1994) J Mol Biol 236: 590
Maltodextrin-Dependent Crystallization of Cyclomaltodextrin Glucanotransferase from Bacillus Circulans Lawson, C.L.L., Bergsma, J., Bruinenberg, P.M., De Vries, G., Dijkhuizen, L., Dijkstra, B.W. (1990) J Mol Biol 214: 807
Organizational Affiliation:
BIOSON Research Institute, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands.
Download Mendeley
