2gci
From Proteopedia
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The 1,1-proton transfer reaction mechanism by alpha-methylacyl-CoA racemase is catalyzed by an asparte/histidine pair and involves a smooth, methionine-rich surface for binding the fatty acyl moiety
Overview
Alpha-methylacyl-CoA racemases are essential enzymes for branched-chain fatty acid metabolism. Their reaction mechanism and the structural basis of their wide substrate specificity are poorly understood. High-resolution crystal structures of Mycobacterium tuberculosis alpha-methylacyl-CoA racemase (MCR) complexed with substrate molecules show the active site geometry required for catalysis of the interconversion of (2S) and (2R)-methylacyl-CoA. The thioester oxygen atom and the 2-methyl group are in a cis-conformation with respect to each other. The thioester oxygen atom fits into an oxyanion hole and the 2-methyl group points into a hydrophobic pocket. The active site geometry agrees with a 1,1-proton transfer mechanism in which the acid/base-pair residues are His126 and Asp156. The structures of the complexes indicate that the acyl chains of the S-substrate and the R-substrate bind in an S-pocket and an R-pocket, respectively. A unique feature of MCR is a large number of methionine residues in the acyl binding region, located between the S-pocket and the R-pocket. It appears that the (S) to (R) interconversion of the 2-methylacyl chiral center is coupled to a movement of the acyl group over this hydrophobic, methionine-rich surface, when moving from its S-pocket to its R-pocket, whereas the 2-methyl moiety and the CoA group remain fixed in their respective pockets.
About this Structure
2GCI is a Single protein structure of sequence from Mycobacterium tuberculosis with and as ligands. Active as Alpha-methylacyl-CoA racemase, with EC number 5.1.99.4 Full crystallographic information is available from OCA.
Reference
The catalysis of the 1,1-proton transfer by alpha-methyl-acyl-CoA racemase is coupled to a movement of the fatty acyl moiety over a hydrophobic, methionine-rich surface., Bhaumik P, Schmitz W, Hassinen A, Hiltunen JK, Conzelmann E, Wierenga RK, J Mol Biol. 2007 Apr 6;367(4):1145-61. Epub 2007 Jan 27. PMID:17320106
Page seeded by OCA on Thu Feb 21 17:30:21 2008
