'''Crystal Structure of Se-Met Methylmalonyl-CoA Epimerase'''
===Crystal Structure of Se-Met Methylmalonyl-CoA Epimerase===
==Overview==
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BACKGROUND: Methylmalonyl-CoA epimerase (MMCE) is an essential enzyme in the breakdown of odd-numbered fatty acids and of the amino acids valine, isoleucine, and methionine. Present in many bacteria and in animals, it catalyzes the conversion of (2R)-methylmalonyl-CoA to (2S)-methylmalonyl-CoA, the substrate for the B12-dependent enzyme, methylmalonyl-CoA mutase. Defects in this pathway can result in severe acidosis and cause damage to the central nervous system in humans. RESULTS: The crystal structure of MMCE from Propionibacterium shermanii has been determined at 2.0 A resolution. The MMCE monomer is folded into two tandem betaalphabetabetabeta modules that pack edge-to-edge to generate an 8-stranded beta sheet. Two monomers then pack back-to-back to create a tightly associated dimer. In each monomer, the beta sheet curves around to create a deep cleft, in the floor of which His12, Gln65, His91, and Glu141 provide a binding site for a divalent metal ion, as shown by the binding of Co2+. Modeling 2-methylmalonate into the active site identifies two glutamate residues as the likely essential bases for the epimerization reaction. CONCLUSIONS: The betaalphabetabetabeta modules of MMCE correspond with those found in several other proteins, including bleomycin resistance protein, glyoxalase I, and a family of extradiol dioxygenases. Differences in connectivity are consistent with the evolution of these very different proteins from a common precursor by mechanisms of gene duplication and domain swapping. The metal binding residues also align precisely, and striking structural similarities between MMCE and glyoxalase I suggest common mechanisms in their respective epimerization and isomerization reactions.
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==About this Structure==
==About this Structure==
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[[Category: Methylmalonyl-coa]]
[[Category: Methylmalonyl-coa]]
[[Category: Vicinal oxygen chelate superfamily]]
[[Category: Vicinal oxygen chelate superfamily]]
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Revision as of 20:00, 1 July 2008
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Crystal structure of methylmalonyl-coenzyme A epimerase from P. shermanii: a novel enzymatic function on an ancient metal binding scaffold., McCarthy AA, Baker HM, Shewry SC, Patchett ML, Baker EN, Structure. 2001 Jul 3;9(7):637-46. PMID:11470438
