1kcl
From Proteopedia
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Bacillus ciruclans strain 251 Cyclodextrin glycosyl transferase mutant G179L
Overview
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.
About this Structure
1KCL is a Single protein structure of sequence from Bacillus circulans with MAL, GLC, CA and MPD as ligands. Active as Cyclomaltodextrin glucanotransferase, with EC number 2.4.1.19 Full crystallographic information is available from OCA.
Reference
The remote substrate binding subsite -6 in cyclodextrin-glycosyltransferase controls the transferase activity of the enzyme via an induced-fit mechanism., Leemhuis H, Uitdehaag JC, Rozeboom HJ, Dijkstra BW, Dijkhuizen L, J Biol Chem. 2002 Jan 11;277(2):1113-9. Epub 2001 Nov 5. PMID:11696539
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