3kuv

Publication Abstract from PubMed

The thioesterase FlK from the fluoroacetate-producing Streptomyces cattleya catalyzes the hydrolysis of fluoroacetyl-coenzyme A. This provides an effective self-defense mechanism, preventing any fluoroacetyl-coenzyme A formed from being further metabolized to 4-hydroxy-trans-aconitate, a lethal inhibitor of the tricarboxylic acid cycle. Remarkably, FlK does not accept acetyl-coenzyme A as a substrate. Crystal structure analysis shows that FlK forms a dimer, in which each subunit adopts a hot dog fold as observed for type II thioesterases. Unlike other type II thioesterases, which invariably utilize either an aspartate or a glutamate as catalytic base, we show by site-directed mutagenesis and crystallography that FlK employs a catalytic triad composed of Thr(42), His(76), and a water molecule, analogous to the Ser/Cys-His-acid triad of type I thioesterases. Structural comparison of FlK complexed with various substrate analogues suggests that the interaction between the fluorine of the substrate and the side chain of Arg(120) located opposite to the catalytic triad is essential for correct coordination of the substrate at the active site and therefore accounts for the substrate specificity.

Structural basis for the activity and substrate specificity of fluoroacetyl-CoA thioesterase FlK.,Dias MV, Huang F, Chirgadze DY, Tosin M, Spiteller D, Dry EF, Leadlay PF, Spencer JB, Blundell TL J Biol Chem. 2010 Jul 16;285(29):22495-504. Epub 2010 Apr 29. PMID:20430898^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.