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| | {{STRUCTURE_1uc4| PDB=1uc4 | SCENE= }} | | {{STRUCTURE_1uc4| PDB=1uc4 | SCENE= }} |
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| - | '''Structure of diol dehydratase complexed with (S)-1,2-propanediol'''
| + | ===Structure of diol dehydratase complexed with (S)-1,2-propanediol=== |
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| - | ==Overview==
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| - | Adenosylcobalamin-dependent diol dehydratase of Klebsiella oxytoca is apparently not stereospecific and catalyzes the conversion of both (R)- and (S)-1,2-propanediol to propionaldehyde. To explain this unusual property of the enzyme, we analyzed the crystal structures of diol dehydratase in complexes with cyanocobalamin and (R)- or (S)-1,2-propanediol. (R)- and (S)-isomers are bound in a symmetrical manner, although the hydrogen-bonding interactions between the substrate and the active-site residues are the same. From the position of the adenosyl radical in the modeled "distal" conformation, it is reasonable for the radical to abstract the pro-R and pro-S hydrogens from (R)- and (S)-isomers, respectively. The hydroxyl groups in the substrate radicals would migrates from C(2) to C(1) by a suprafacial shift, resulting in the stereochemical inversion at C(1). This causes 60 degrees clockwise and 70 degrees counterclockwise rotations of the C(1)-C(2) bond of the (R)- and (S)-isomers, respectively, if viewed from K+. A modeling study of 1,1-gem-diol intermediates indicated that new radical center C(2) becomes close to the methyl group of 5'-deoxyadenosine. Thus, the hydrogen back-abstraction (recombination) from 5'-deoxyadenosine by the product radical is structurally feasible. It was also predictable that the substitution of the migrating hydroxyl group by a hydrogen atom from 5'-deoxyadenosine takes place with the inversion of the configuration at C(2) of the substrate. Stereospecific dehydration of the 1,1-gem-diol intermediates can also be rationalized by assuming that Asp-alpha335 and Glu-alpha170 function as base catalysts in the dehydration of the (R)- and (S)-isomers, respectively. The structure-based mechanism and stereochemical courses of the reaction are proposed.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_12684496}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 12684496 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_12684496}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Yasuoka, N.]] | | [[Category: Yasuoka, N.]] |
| | [[Category: Alpha/beta barrel]] | | [[Category: Alpha/beta barrel]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 11:01:32 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 04:18:09 2008'' |
Revision as of 01:18, 29 July 2008
Template:STRUCTURE 1uc4
Structure of diol dehydratase complexed with (S)-1,2-propanediol
Template:ABSTRACT PUBMED 12684496
About this Structure
1UC4 is a Protein complex structure of sequences from Klebsiella oxytoca. Full crystallographic information is available from OCA.
Reference
Structural rationalization for the lack of stereospecificity in coenzyme B12-dependent diol dehydratase., Shibata N, Nakanishi Y, Fukuoka M, Yamanishi M, Yasuoka N, Toraya T, J Biol Chem. 2003 Jun 20;278(25):22717-25. Epub 2003 Apr 8. PMID:12684496
Page seeded by OCA on Tue Jul 29 04:18:09 2008
