View source for 2gce

[[Image:2gce.gif|left|200px]]

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{{STRUCTURE_2gce|  PDB=2gce  |  SCENE=  }} 

'''The 1,1-proton transfer reaction mechanism by alpha-methylacyl-CoA racemase is catalyzed by an aspartate/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==
2GCE is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Mycobacterium_tuberculosis Mycobacterium tuberculosis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2GCE 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:[http://www.ncbi.nlm.nih.gov/pubmed/17320106 17320106]
[[Category: Alpha-methylacyl-CoA racemase]]
[[Category: Mycobacterium tuberculosis]]
[[Category: Single protein]]
[[Category: Bhaumik, P.]]
[[Category: Wierenga, R K.]]
[[Category: Alpha-methylacyl-coa racemase]]
[[Category: Coa transferase]]
[[Category: Coenzyme some]]
[[Category: Proton transfer]]
[[Category: Racemase]]
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