1kcl
From Proteopedia
(New page: 200px<br /><applet load="1kcl" size="450" color="white" frame="true" align="right" spinBox="true" caption="1kcl, resolution 1.94Å" /> '''Bacillus ciruclans s...) |
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| - | [[Image:1kcl.jpg|left|200px]]<br /><applet load="1kcl" size=" | + | [[Image:1kcl.jpg|left|200px]]<br /><applet load="1kcl" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1kcl, resolution 1.94Å" /> | caption="1kcl, resolution 1.94Å" /> | ||
'''Bacillus ciruclans strain 251 Cyclodextrin glycosyl transferase mutant G179L'''<br /> | '''Bacillus ciruclans strain 251 Cyclodextrin glycosyl transferase mutant G179L'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Cyclodextrin-glycosyltransferase (CGTase) catalyzes the formation of | + | 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== | ==About this Structure== | ||
| - | 1KCL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_circulans Bacillus circulans] with MAL, GLC, CA and MPD as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Cyclomaltodextrin_glucanotransferase Cyclomaltodextrin glucanotransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.19 2.4.1.19] Full crystallographic information is available from [http:// | + | 1KCL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_circulans Bacillus circulans] with <scene name='pdbligand=MAL:'>MAL</scene>, <scene name='pdbligand=GLC:'>GLC</scene>, <scene name='pdbligand=CA:'>CA</scene> and <scene name='pdbligand=MPD:'>MPD</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Cyclomaltodextrin_glucanotransferase Cyclomaltodextrin glucanotransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.19 2.4.1.19] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1KCL OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Cyclomaltodextrin glucanotransferase]] | [[Category: Cyclomaltodextrin glucanotransferase]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Dijkstra, B | + | [[Category: Dijkstra, B W.]] |
| - | [[Category: Rozeboom, H | + | [[Category: Rozeboom, H J.]] |
| - | [[Category: Uitdehaag, J | + | [[Category: Uitdehaag, J C.M.]] |
[[Category: CA]] | [[Category: CA]] | ||
[[Category: GLC]] | [[Category: GLC]] | ||
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[[Category: transferase]] | [[Category: transferase]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:32:33 2008'' |
Revision as of 11:32, 21 February 2008
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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 , , and 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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