Crystal structure of Pseudomonas aeruginosa FabB C161A, a template for structure-based design for new antibiotics.

Background : FabB (3-oxoacyl-[acyl-carrier-protein] synthase 1) is part of the fatty acid synthesis II pathway found in bacteria and a potential target for antibiotics. The enzyme catalyses the Claisen condensation of malonyl-ACP (acyl carrier protein) with acyl-ACP via an acyl-enzyme intermediate. Here, we report the crystal structure of the intermediate-mimicking Pseudomonas aeruginosa FabB ( Pa FabB) C161A variant. Methods : His-tagged Pa FabB C161A was expressed in E. coli Rosetta DE3 pLysS cells, cleaved by TEV protease and purified using affinity and size exclusion chromatography. Commercial screens were used to identify suitable crystallization conditions which were subsequently improved to obtain well diffracting crystals. Results : We developed a robust and efficient system for recombinant expression of Pa FabB C161A. Conditions to obtain well diffracting crystals were established. The crystal structure of Pa FabB C161A was solved by molecular replacement at 1.3 Å resolution. Binding site comparison between Pa FabB and Pa FabF revealed a conserved malonyl binding site but differences in the fatty acid binding channel. Conclusions : The Pa FabB C161A crystal structure can be used as a template to facilitate the design of FabB inhibitors.