Crystal structure of the Escherichia coli thioesterase II, a homolog of the human Nef binding enzyme

Here we report the solution and refinement at 1.9 Angstrom resolution of th e crystal structure of the Escherichia coli medium chain length acyl-CoA th ioesterase II. This enzyme is a close homolog of the human protein that int eracts with the product of the HIV-1 Nef gene, sharing 45% amino acid seque nce identity with it. The structure of the a coli thioesterase II reveals a new tertiary fold, a 'double hot dog: showing an internal repeat with a ba sic unit that is structurally similar to the recently described beta-hydrox ydecanoyl thiol ester dehydrase, The catalytic site, inferred from the crys tal structure and verified by site directed mutagenesis, involves novel che mistry and includes Asp 204, Gin 278 and Thr 228, which synergistically act ivate a nucleophilic water molecule.