title: The missing piece of the type II fatty acid synthase system from Mycobacterium tuberculosis.
abstract: The Mycobacterium tuberculosis fatty acid synthase type II (FAS-II) system has the unique property of producing unusually long-chain fatty acids involved in the biosynthesis of mycolic acids, key molecules of the tubercle bacillus. The enzyme(s) responsible for dehydration of (3R)-hydroxyacyl-ACP during the elongation cycles of the mycobacterial FAS-II remained unknown. This step is classically catalyzed by FabZ- and FabA-type enzymes in bacteria, but no such proteins are present in mycobacteria. Bioinformatic analyses and an essentiality study allowed the identification of a candidate protein cluster, Rv0635-Rv0636-Rv0637. Its expression in recombinant Escherichia coli strains leads to the formation of two heterodimers, Rv0635-Rv0636 (HadAB) and Rv0636-Rv0637 (HadBC), which also occurs in Mycobacterium smegmatis, as shown by split-Trp assays. Both heterodimers exhibit the enzymatic properties expected for mycobacterial FAS-II dehydratases: a marked specificity for both long-chain (>or=C(12)) and ACP-linked substrates. Furthermore, they function as 3-hydroxyacyl dehydratases when coupled with MabA and InhA enzymes from the M. tuberculosis FAS-II system. HadAB and HadBC are the long-sought (3R)-hydroxyacyl-ACP dehydratases. The correlation between the substrate specificities of these enzymes, the organization of the orthologous gene cluster in different Corynebacterineae, and the structure of their mycolic acids suggests distinct roles for both heterodimers during the elongation process. This work describes bacterial monofunctional (3R)-hydroxyacyl-ACP dehydratases belonging to the hydratase 2 family. Their original structure and the fact that they are essential for M. tuberculosis survival make these enzymes very good candidates for the development of antimycobacterial drugs.
authors.affiliation: *Département des Mécanismes Moléculaires des Infections Mycobactériennes, Institut de Pharmacologie et de Biologie Structurale, Centre National de la Recherche Scientifique, 31077 Toulouse, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Sacco
authors.forename: Adrian Suarez
authors.initials: AS
authors.lastname: Covarrubias
authors.forename: Helen M
authors.initials: HM
authors.lastname: O'Hare
authors.forename: Paul
authors.initials: P
authors.lastname: Carroll
authors.forename: Nathalie
authors.initials: N
authors.lastname: Eynard
authors.forename: T Alwyn
authors.initials: TA
authors.lastname: Jones
authors.forename: Tanya
authors.initials: T
authors.lastname: Parish
authors.forename: Mamadou
authors.initials: M
authors.lastname: Daffé
authors.forename: Kristina
authors.initials: K
authors.lastname: Bäckbro
authors.forename: Annaïk
authors.initials: A
authors.lastname: Quémard
mesh_terms: D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D002384:Catalysis; D003198:Computer Simulation; D004926:Escherichia coli / Q000235:genetics; D054889:Fatty Acid Synthase, Type II; D064429:Fatty Acid Synthases / Q000235:genetics / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D006639:Histidine / Q000378:metabolism; D006836:Hydro-Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D013058:Mass Spectrometry; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics; D009171:Mycolic Acids / Q000737:chemistry / Q000378:metabolism; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000378:metabolism; D020539:Sequence Analysis, Protein; D013379:Substrate Specificity