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1iwp

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[[Image:1iwp.jpg|left|200px]]
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{{STRUCTURE_1iwp| PDB=1iwp | SCENE= }}
{{STRUCTURE_1iwp| PDB=1iwp | SCENE= }}
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'''Glycerol Dehydratase-cyanocobalamin Complex of Klebsiella pneumoniae'''
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===Glycerol Dehydratase-cyanocobalamin Complex of Klebsiella pneumoniae===
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==Overview==
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Recombinant glycerol dehydratase of Klebsiella pneumoniae was purified to homogeneity. The subunit composition of the enzyme was most probably alpha 2 beta 2 gamma 2. When (R)- and (S)-propane-1,2-diols were used independently as substrates, the rate with the (R)-enantiomer was 2.5 times faster than that with the (S)-isomer. In contrast to diol dehydratase, an isofunctional enzyme, the affinity of the enzyme for the (S)-isomer was essentially the same or only slightly higher than that for the (R)-isomer (Km(R)/Km(S) = 1.5). The crystal structure of glycerol dehydratase in complex with cyanocobalamin and propane-1,2-diol was determined at 2.1 A resolution. The enzyme exists as a dimer of the alpha beta gamma heterotrimer. Cobalamin is bound at the interface between the alpha and beta subunits in the so-called 'base-on' mode with 5,6-dimethylbenzimidazole of the nucleotide moiety coordinating to the cobalt atom. The electron density of the cyano group was almost unobservable, suggesting that the cyanocobalamin was reduced to cob(II)alamin by X-ray irradiation. The active site is in a (beta/alpha)8 barrel that was formed by a central region of the alpha subunit. The substrate propane-1,2-diol and essential cofactor K+ are bound inside the (beta/alpha)8 barrel above the corrin ring of cobalamin. K+ is hepta-coordinated by the two hydroxyls of the substrate and five oxygen atoms from the active-site residues. These structural features are quite similar to those of diol dehydratase. A closer contact between the alpha and beta subunits in glycerol dehydratase may be reminiscent of the higher affinity of the enzyme for adenosylcobalamin than that of diol dehydratase. Although racemic propane-1,2-diol was used for crystallization, the substrate bound to glycerol dehydratase was assigned to the (R)-isomer. This is in clear contrast to diol dehydratase and accounts for the difference between the two enzymes in the susceptibility of suicide inactivation by glycerol.
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{{ABSTRACT_PUBMED_12230560}}
==About this Structure==
==About this Structure==
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[[Category: Klebsiella pneumoniae]]
[[Category: Klebsiella pneumoniae]]
[[Category: Radical catalysis]]
[[Category: Radical catalysis]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 14:08:21 2008''

Revision as of 11:08, 1 July 2008

Image:1iwp.png

Template:STRUCTURE 1iwp

Glycerol Dehydratase-cyanocobalamin Complex of Klebsiella pneumoniae

Template:ABSTRACT PUBMED 12230560

About this Structure

1IWP is a Protein complex structure of sequences from Klebsiella pneumoniae. Full crystallographic information is available from OCA.

Reference

The crystal structure of coenzyme B12-dependent glycerol dehydratase in complex with cobalamin and propane-1,2-diol., Yamanishi M, Yunoki M, Tobimatsu T, Sato H, Matsui J, Dokiya A, Iuchi Y, Oe K, Suto K, Shibata N, Morimoto Y, Yasuoka N, Toraya T, Eur J Biochem. 2002 Sep;269(18):4484-94. PMID:12230560

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