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Acyl-CoA synthetases belong to the superfamily of adenylate-forming enzymes, and catalyze the two-step activation of fatty acids or carboxylate-containing xenobiotics. The carboxylate substrate first reacts with ATP to form an acyl-adenylate intermediate, which then reacts with CoA to produce an acyl-CoA ester. Here, we report the first crystal structure of a medium-chain acyl-CoA synthetase ACSM2A, in a series of substrate/product/cofactor complexes central to the catalytic mechanism. We observed a substantial rearrangement between the N- and C-terminal domains, driven purely by the identity of the bound ligand in the active site. Our structures allowed us to identify the presence or absence of the ATP pyrophosphates as the conformational switch, and elucidated new mechanistic details, including the role of invariant Lys557 and a divalent magnesium ion in coordinating the ATP pyrophosphates, as well as the involvement of a Gly-rich P-loop and the conserved Arg472-Glu365 salt bridge in the domain rearrangement.

Original publication

DOI

10.1016/j.jmb.2009.03.064

Type

Journal article

Journal

J Mol Biol

Publication Date

22/05/2009

Volume

388

Pages

997 - 1008

Keywords

Adenosine Monophosphate, Adenosine Triphosphate, Amino Acid Sequence, Binding Sites, Catalysis, Coenzyme A, Coenzyme A Ligases, Crystallography, X-Ray, Fatty Acids, Humans, Isoenzymes, Models, Molecular, Molecular Conformation, Molecular Sequence Data, Protein Conformation, Sequence Alignment, Substrate Specificity