title: Improved thermostability of bacillus circulans cyclodextrin glycosyltransferase by the introduction of a salt bridge.
abstract: Cyclodextrin glycosyltransferase (CGTase) catalyzes the formation of cyclodextrins from starch. Among the CGTases with known three-dimensional structure, Thermoanaerobacterium thermosulfurigenes CGTase has the highest thermostability. By replacing amino acid residues in the B-domain of Bacillus circulans CGTase with those from T. thermosulfurigenes CGTase, we identified a B. circulans CGTase mutant (with N188D and K192R mutations), with a strongly increased activity half-life at 60 degrees C. Asp188 and Arg192 form a salt bridge in T. thermosulfurigenes CGTase. Structural analysis of the B. circulans CGTase mutant revealed that this salt bridge is also formed in the mutant. Thus, the activity half-life of this enzyme can be enhanced by rational protein engineering.
authors.affiliation: Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
authors.forename: Hans
authors.initials: H
authors.lastname: Leemhuis
authors.forename: Henriëtte J
authors.initials: HJ
authors.lastname: Rozeboom
authors.forename: Bauke W
authors.initials: BW
authors.lastname: Dijkstra
authors.forename: Lubbert
authors.initials: L
authors.lastname: Dijkhuizen
mesh_terms: D001120:Arginine / Q000737:chemistry; D001224:Aspartic Acid / Q000737:chemistry; D001407:Bacillus / Q000201:enzymology*; D002152:Calorimetry, Differential Scanning; D018360:Crystallography, X-Ray; D004795:Enzyme Stability; D005964:Glucosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006207:Half-Life; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D012492:Salts / Q000737:chemistry; D013696:Temperature
chemical_list: D012492:Salts; D001224:Aspartic Acid; D001120:Arginine; D005964:Glucosyltransferases; C019963:cyclomaltodextrin glucanotransferase