1KCK

Bacillus circulans strain 251 Cyclodextrin glycosyl transferase mutant N193G

Summary for 1KCK

• Entry DOI: 10.2210/pdb1kck/pdb
• Related: 1cdg 1kcl
• Related PRD ID: PRD_900001 PRD_900009 PRD_900065
• Descriptor: CYCLODEXTRIN GLYCOSYLTRANSFERASE, alpha-D-quinovopyranose-(1-4)-alpha-D-glucopyranose, alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, ... (9 entities in total)
• Functional Keywords: glycosyl transferase, transferase, cylcodextrin, acarbose
• Biological source: Bacillus circulans
• Total number of polymer chains: 1
• Total formula weight: 76615.40

Authors

Rozeboom, H.J.,Uitdehaag, J.C.M.,Dijkstra, B.W. (deposition date: 2001-11-09, release date: 2002-01-16, Last modification date: 2024-10-30)

Primary citation

Leemhuis, H.,Uitdehaag, J.C.,Rozeboom, H.J.,Dijkstra, B.W.,Dijkhuizen, L.
The remote substrate binding subsite -6 in cyclodextrin-glycosyltransferase controls the transferase activity of the enzyme via an induced-fit mechanism.
J.Biol.Chem., 277:1113-1119, 2002

PubMed Abstract: Cyclodextrin-glycosyltransferase (CGTase) catalyzes the formation of alpha-, beta-, and gamma-cyclodextrins (cyclic alpha-(1,4)-linked oligosaccharides of 6, 7, or 8 glucose residues, respectively) from starch. Nine substrate binding subsites were observed in an x-ray structure of the CGTase from Bacillus circulans strain 251 complexed with a maltononaose substrate. Subsite -6 is conserved in CGTases, suggesting its importance for the reactions catalyzed by the enzyme. To investigate this in detail, we made six mutant CGTases (Y167F, G179L, G180L, N193G, N193L, and G179L/G180L). All subsite -6 mutants had decreased k(cat) values for beta-cyclodextrin formation, as well as for the disproportionation and coupling reactions, but not for hydrolysis. Especially G179L, G180L, and G179L/G180L affected the transglycosylation activities, most prominently for the coupling reactions. The results demonstrate that (i) subsite -6 is important for all three CGTase-catalyzed transglycosylation reactions, (ii) Gly-180 is conserved because of its importance for the circularization of the linear substrates, (iii) it is possible to independently change cyclization and coupling activities, and (iv) substrate interactions at subsite -6 activate the enzyme in catalysis via an induced-fit mechanism. This article provides for the first time definite biochemical evidence for such an induced-fit mechanism in the alpha-amylase family.

PubMed: 11696539
DOI: 10.1074/jbc.M106667200

Experimental method

X-RAY DIFFRACTION (2.43 Å)