'''Structure of diol dehydratase complexed with (R)-1,2-propanediol'''
===Structure of diol dehydratase complexed with (R)-1,2-propanediol===
==Overview==
<!--
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.
-->
{{ABSTRACT_PUBMED_12684496}}
==About this Structure==
==About this Structure==
Line 30:
Line 34:
[[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 11:01:33 2008''
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 07:47:33 2008''
Revision as of 04:47, 28 July 2008
This article has been automatically seeded. Changes to this page should pertain to the PDB entry only and not to the protein or biomolecule in general.
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
