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| [[Image:1cgu.jpg|left|200px]] | | {{Seed}} |
| | [[Image:1cgu.png|left|200px]] |
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| {{STRUCTURE_1cgu| PDB=1cgu | SCENE= }} | | {{STRUCTURE_1cgu| PDB=1cgu | SCENE= }} |
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| '''CATALYTIC CENTER OF CYCLODEXTRIN GLYCOSYLTRANSFERASE DERIVED FROM X-RAY STRUCTURE ANALYSIS COMBINED WITH SITE-DIRECTED MUTAGENESIS'''
| | ===CATALYTIC CENTER OF CYCLODEXTRIN GLYCOSYLTRANSFERASE DERIVED FROM X-RAY STRUCTURE ANALYSIS COMBINED WITH SITE-DIRECTED MUTAGENESIS=== |
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| ==Overview==
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| An X-ray structure analysis of a crystal of mutant Asp229----Ala of cyclodextrin glycosyltransferase from Bacillus circulans (Ec 2.4.1.19) that had been shortly exposed to beta-cyclodextrin showed density corresponding to a maltose bound at the catalytic center. The crystal structure was refined to an R-factor of 18.7% at 2.5-A resolution. The catalytic center is defined by homology with the structurally known alpha-amylases and by the observation that mutants Asp229----Ala and Asp328----Ala are almost inactive. By model building, the density-defined maltose was extended to a full beta-cyclodextrin, which then indicated the general locations of seven subsites for glucosyl units. The catalytically competent residues Asp229, Glu257, and Asp328 are at the reducing end of the density-defined maltose. In the unligated wild-type structure, Glu257 and Asp328 form a 2.6-A hydrogen bond between their carboxylates in an arrangement that resembles those of the catalytically competent carboxylates in acid proteases. Presumably, the first catalytic step is an attack of the proton between Glu257 and Asp328 on the oxygen of the glycosidic bond.
| | The line below this paragraph, {{ABSTRACT_PUBMED_1390660}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 1390660 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_1390660}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Schulz, G E.]] | | [[Category: Schulz, G E.]] |
| [[Category: Glycosyltransferase]] | | [[Category: Glycosyltransferase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 12:43:17 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 20:43:53 2008'' |
