Enoyl-acyl carrier protein (ACP) reductases (ENRs) are enzymes involved in the final reduction in the bacterial fatty acid biosynthesis (FAS II) pathway. Based on their amino-acid sequences, ENRs have been classified as FabI, FabK, FabL, and FabV. Among them, FabI is highly conserved among most bacteria and many ligands have been designed and tested for their inhibitory activities against FabI. In this study, we report crystal structures of FabI from Pseudomonas aeruginosa (PaFabI) in its apo and ternary complex with NAD + and triclosan at 2.6 and 1.8 Å resolutions, respectively. Structural comparison with apo and ternary complex indicates that triclosan leads to ordering of the substrate-binding loop like other previously reported FabI structures. Depending on the conformations of the substrate-binding loop, there are variations in the binding affinity of FabI and triclosan. PaFabI displays a relatively higher affinity toward triclosan in comparison with other FabIs, and this corresponds to its conformation of the substrate-binding loop.

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Enoyl-(acyl-carrier protein) reductase (ENR) catalyzes the last step of the fattyacid elongation cycle of the bacterial fatty-acid biosynthesis (FAS II) pathway. Recently, a new class of ENR has been identified from Vibrio cholerae and was named FabV. In order to understand the molecular mechanism of the new class of ENR at the structural level, FabV from V. fischeri was overexpressed, purified and crystallized. Diffraction data were collected to 2.7 Å resolution from a native crystal. The crystal belonged to the orthorhombic space group P2 1 2 1 2, with unit-cell parameters a = 123.53, b = 164.14, c = 97.07 Å . The presence of four molecules of FabV in the asymmetric unit gave a V M value of 2.81 Å 3 Da À1, with a corresponding solvent content of 54.5%.

During fatty-acid biosynthesis, enoyl-acyl carrier protein (enoyl-ACP) reductase catalyzes the reduction of trans-2-enoyl-ACP to fully saturated acyl-ACP via the ubiquitous fatty-acid synthase system. NADH-dependent enoyl-ACP reductase (FabI) from Pseudomonas aeruginosa has been purified and crystallized as an apoenzyme and in a complex form with NADH and triclosan. Triclosan is an inhibitor of FabI and forms a stable ternary complex in the presence of NADH. The crystals of native and complexed FabI diffracted to resolutions of 2.6 and 1.8 Å , respectively. The crystals both belonged to space group

Nitroalkane oxidase (NAO) is a flavin-dependent enzyme which catalyses the oxidation of nitroalkanes to the corresponding aldehydes or ketones, nitrite and hydrogen peroxide. In order to better understand the structure and function of this enzyme, NAO from Pseudomonas aeruginosa was purified and crystallized as a native and a selenomethionine-substituted (SeMet) enzyme. Both crystals diffracted to a resolution of 1.9 Å and belonged to the primitive orthorhombic space group P2 1 , with unit-cell parameters a = 70.06, b = 55.43, c = 87.74 Å , = 96.56 for native NAO and a = 69.89, b = 54.83, c = 88.20 Å , = 95.79 for SeMet NAO. Assuming the presence of two molecules in the asymmetric unit in both crystals, the Matthews coefficients (V M ) for native and SeMet NAO were calculated to be 2.30 and 2.48 Å 3 Da À1 , with estimated solvent contents of 46.50 and 50.37%, respectively.