Download MendeleyThe cyclization mechanism of cyclodextrin glycosyltransferase (CGTase) as revealed by a gamma-cyclodextrin-CGTase complex at 1.8-A resolution.
Uitdehaag, J.C., Kalk, K.H., van Der Veen, B.A., Dijkhuizen, L., Dijkstra, B.W.(1999) J Biol Chem 274: 34868-34876
- PubMed: 10574960
- DOI: https://doi.org/10.1074/jbc.274.49.34868
- Primary Citation of Related Structures:
1D3C - PubMed Abstract:
The enzyme cyclodextrin glycosyltransferase is closely related to alpha-amylases but has the unique ability to produce cyclodextrins (circular alpha(1-->4)-linked glucoses) from starch. To characterize this specificity we determined a 1.8-A structure of an E257Q/D229N mutant cyclodextrin glycosyltransferase in complex with its product gamma-cyclodextrin, which reveals for the first time how cyclodextrin is competently bound. Across subsites -2, -1, and +1, the cyclodextrin ring binds in a twisted mode similar to linear sugars, giving rise to deformation of its circular symmetry. At subsites -3 and +2, the cyclodextrin binds in a manner different from linear sugars. Sequence comparisons and site-directed mutagenesis experiments support the conclusion that subsites -3 and +2 confer the cyclization activity in addition to subsite -6 and Tyr-195. On this basis, a role of the individual residues during the cyclization reaction cycle is proposed.
Organizational Affiliation:
BIOSON Research Institute, Laboratory of Biophysical Chemistry, Groningen Biomolecular Sciences, University of Groningen, Nijenborgh 4, 9747AG Groningen, the Netherlands.
