title: Structural elucidation of the specificity of the antibacterial agent triclosan for malarial enoyl acyl carrier protein reductase.
abstract: The human malaria parasite Plasmodium falciparum synthesizes fatty acids using a type II pathway that is absent in humans. The final step in fatty acid elongation is catalyzed by enoyl acyl carrier protein reductase, a validated antimicrobial drug target. Here, we report the cloning and expression of the P. falciparum enoyl acyl carrier protein reductase gene, which encodes a 50-kDa protein (PfENR) predicted to target to the unique parasite apicoplast. Purified PfENR was crystallized, and its structure resolved as a binary complex with NADH, a ternary complex with triclosan and NAD(+), and as ternary complexes bound to the triclosan analogs 1 and 2 with NADH. Novel structural features were identified in the PfENR binding loop region that most closely resembled bacterial homologs; elsewhere the protein was similar to ENR from the plant Brassica napus (root mean square for Calphas, 0.30 A). Triclosan and its analogs 1 and 2 killed multidrug-resistant strains of intra-erythrocytic P. falciparum parasites at sub to low micromolar concentrations in vitro. These data define the structural basis of triclosan binding to PfENR and will facilitate structure-based optimization of PfENR inhibitors.
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA.
authors.forename: Remo
authors.initials: R
authors.lastname: Perozzo
authors.forename: Mack
authors.initials: M
authors.lastname: Kuo
authors.forename: Amar bir Singh
authors.initials: Ab
authors.lastname: Sidhu
authors.forename: Jacob T
authors.initials: JT
authors.lastname: Valiyaveettil
authors.forename: Robert
authors.initials: R
authors.lastname: Bittman
authors.forename: William R
authors.initials: WR
authors.lastname: Jacobs
authors.forename: David A
authors.initials: DA
authors.lastname: Fidock
authors.forename: James C
authors.initials: JC
authors.lastname: Sacchettini
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH); D008958:Models, Molecular; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000201:enzymology*; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014260:Triclosan / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000890:Anti-Infective Agents; D017931:DNA Primers; D014260:Triclosan; D010088:Oxidoreductases; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH)