title: Crystal structures and kinetic properties of enoyl-acyl carrier protein reductase I from Candidatus Liberibacter asiaticus.
abstract: Huanglongbing (HLB) is a destructive citrus disease. The leading cause of HLB is Candidatus Liberibacter asiaticus. Fatty acid biosynthesis is essential for bacterial viability and has been validated as a target for the discovery of novel antibacterial agents. Enoyl-acyl carrier protein reductase (also called ENR or FabI and a product of the fabI gene) is an enzyme required in a critical step of bacterial fatty acid biosynthesis and has attracted attention as a target of novel antimicrobial agents. We determined the crystal structures of FabI from Ca. L. asiaticus in its apoform as well as in complex with b-nicotinamide adenine dinucleotide (NAD) at 1.7 and 2.7 Å resolution, respectively, to facilitate the design and screening of small molecule inhibitors of FabI. The monomeric ClFabI is highly similar to other known FabI structures as expected; however, unlike the typical tetramer, ClFabI exists as a hexamer in crystal, whereas as dimer in solution, on the other hand, the substrate binding loop which always disordered in apoform FabI structures is ordered in apo-ClFabI. Interestingly, the structure of ClFabI undergoes remarkable conformational change in the substrate-binding loop in the presence of NAD. We conclude that the signature sequence motif of FabI can be considered as Gly-(Xaa)5-Ser-(Xaa)n-Val-Tyr-(Xaa)6-Lys-(Xaa)n-Thr instead of Tyr-(Xaa)6-Lys. We have further identified isoniazid as a competitive inhibitor with NADH.
authors.affiliation: Ministry of Education Key Laboratory of Plant Biology, Department of Horticulture and Forestry, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Jiang
authors.forename: Zengqiang
authors.initials: Z
authors.lastname: Gao
authors.forename: Yanhua
authors.initials: Y
authors.lastname: Li
authors.forename: Shennan
authors.initials: S
authors.lastname: Wang
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Dong
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH) / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D011487:Protein Conformation; D012230:Rhizobiaceae / Q000201:enzymology*
chemical_list: D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH)
keywords: Candidatus Liberibacter asiaticus; b-nicotinamide adenine dinucleotide; crystal structures; enoyl-acyl carrier protein reductase I; isoniazid