Crystal structure of beta-ketoacyl-acyl carrier protein synthase II from E.coli reveals the molecular architecture of condensing enzymes.
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Huang W, Jia J, Edwards P, Dehesh K, Schneider G, Lindqvist Y
Crystal structure of beta-ketoacyl-acyl carrier protein synthase II from E.coli reveals the molecular architecture of condensing enzymes.
EMBO J. 1998 Mar 2;17(5):1183-91.
- PubMed ID
- 9482715 [ View in PubMed]
- Abstract
In the biosynthesis of fatty acids, the beta-ketoacyl-acyl carrier protein (ACP) synthases catalyze chain elongation by the addition of two-carbon units derived from malonyl-ACP to an acyl group bound to either ACP or CoA. The crystal structure of beta-ketoacyl synthase II from Escherichia coli has been determined with the multiple isomorphous replacement method and refined at 2.4 A resolution. The subunit consists of two mixed five-stranded beta-sheets surrounded by alpha-helices. The two sheets are packed against each other in such a way that the fold can be described as consisting of five layers, alpha-beta-alpha-beta-alpha. The enzyme is a homodimer, and the subunits are related by a crystallographic 2-fold axis. The two active sites are located near the dimer interface but are approximately 25 A apart. The proposed nucleophile in the reaction, Cys163, is located at the bottom of a mainly hydrophobic pocket which is also lined with several conserved polar residues. In spite of very low overall sequence homology, the structure of beta-ketoacyl synthase is similar to that of thiolase, an enzyme involved in the beta-oxidation pathway, indicating that both enzymes might have a common ancestor.