title: Separate entrance and exit portals for ligand traffic in Mycobacterium tuberculosis FabH.
abstract: Mycobacterium tuberculosis FabH initiates type II fatty acid synthase-catalyzed formation of the long chain (C(16)-C(22)) acyl-coenzyme A (CoA) precursors of mycolic acids, which are major constituents of the bacterial cell envelope. Crystal structures of M. tuberculosis FabH (mtFabH) show the substrate binding site to be a buried, extended L-shaped channel with only a single solvent access portal. Entrance of an acyl-CoA substrate through the solvent portal would require energetically unfavorable reptational threading of the substrate to its reactive position. Using a class of FabH inhibitors, we have tested an alternative hypothesis that FabH exists in an "open" form during substrate binding and product release, and a "closed" form in which catalysis and intermediate steps occur. This hypothesis is supported by mass spectrometric analysis of the product profile and crystal structures of complexes of mtFabH with these inhibitors.
authors.affiliation: Department of Chemistry, Portland State University, Portland, OR 97207, USA.
authors.forename: Sarbjot
authors.initials: S
authors.lastname: Sachdeva
authors.forename: Faik N
authors.initials: FN
authors.lastname: Musayev
authors.forename: Mamoun M
authors.initials: MM
authors.lastname: Alhamadsheh
authors.forename: J Neel
authors.initials: JN
authors.lastname: Scarsdale
authors.forename: H Tonie
authors.initials: HT
authors.lastname: Wright
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Reynolds
mesh_terms: D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000214:Acyl Coenzyme A / Q000037:antagonists & inhibitors / Q000378:metabolism; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D057927:Hydrophobic and Hydrophilic Interactions; D008024:Ligands; D008958:Models, Molecular; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D009171:Mycolic Acids / Q000378:metabolism; D011485:Protein Binding; D012997:Solvents / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000214:Acyl Coenzyme A; D004791:Enzyme Inhibitors; D008024:Ligands; D009171:Mycolic Acids; D012997:Solvents; D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase; D003545:Cysteine