1kck
From Proteopedia
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'''Bacillus circulans strain 251 Cyclodextrin glycosyl transferase mutant N193G''' | '''Bacillus circulans strain 251 Cyclodextrin glycosyl transferase mutant N193G''' | ||
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[[Category: Rozeboom, H J.]] | [[Category: Rozeboom, H J.]] | ||
[[Category: Uitdehaag, J C.M.]] | [[Category: Uitdehaag, J C.M.]] | ||
| - | [[Category: | + | [[Category: Acarbose]] |
| - | [[Category: | + | [[Category: Cylcodextrin]] |
| - | [[Category: | + | [[Category: Glycosyl transferase]] |
| - | [[Category: | + | [[Category: Transferase]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 22:34:29 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 19:34, 2 May 2008
Bacillus circulans strain 251 Cyclodextrin glycosyl transferase mutant N193G
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
1KCK is a Single protein structure of sequence from Bacillus circulans. 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 Page seeded by OCA on Fri May 2 22:34:29 2008
