title: Requirement for kasB in Mycobacterium mycolic acid biosynthesis, cell wall impermeability and intracellular survival: implications for therapy.
abstract: Mycobacterium tuberculosis infects one-third of the world's population and causes two million deaths annually. The unusually low permeability of its cell wall contributes to the ability of M. tuberculosis to grow within host macrophages, a property required for pathogenesis of infection. Mycobacterium marinum is an established model for discovering genes involved in mycobacterial infection. Mycobacterium marinum mutants with transposon insertions in the beta-ketoacyl-acyl carrier protein synthase B gene (kasB) grew poorly in macrophages, although growth in vitro was unaffected. Detailed analyses by thin-layer chromatography, nuclear magnetic resonance (NMR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, infrared spectroscopy, and chemical degradations showed that the kasB mutants synthesize mycolic acids that are 2-4 carbons shorter than wild type; the defect was localized to the proximal portion of the meromycolate chain. In addition, these mutants showed a significant (approximately 30%) reduction in the abundance of keto-mycolates, with a slight compensatory increase of both alpha- and methoxy-mycolates. Despite these small changes in mycolate length and composition, the kasB mutants exhibited strikingly altered cell wall permeability, leading to a marked increase in susceptibility to lipophilic antibiotics and the host antimicrobial molecules defensin and lysozyme. The abnormalities of the kasB mutants were fully complemented by expressing M. tuberculosis kasB, but not by the closely related gene kasA. These studies identify kasB as a novel target for therapeutic intervention in mycobacterial diseases.
authors.affiliation: Program in Host-Pathogen Interactions, UCSF Campus Box 2140, 600 16th St, San Francisco, CA 94143-2140, USA.
authors.forename: Lian-Yong
authors.initials: LY
authors.lastname: Gao
authors.forename: Francoise
authors.initials: F
authors.lastname: Laval
authors.forename: Elise H
authors.initials: EH
authors.lastname: Lawson
authors.forename: Richard K
authors.initials: RK
authors.lastname: Groger
authors.forename: Andy
authors.initials: A
authors.lastname: Woodruff
authors.forename: J Hiroshi
authors.initials: JH
authors.lastname: Morisaki
authors.forename: Jeffery S
authors.initials: JS
authors.lastname: Cox
authors.forename: Mamadou
authors.initials: M
authors.lastname: Daffe
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Brown
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002460:Cell Line; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism*; D002569:Cerulenin / Q000494:pharmacology; D002849:Chromatography, Gas; D002855:Chromatography, Thin Layer; D015169:Colony Count, Microbial; D004251:DNA Transposable Elements; D023082:Defensins / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D005816:Genetic Complementation Test; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D009113:Muramidase / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009164:Mycobacterium Infections / Q000235:genetics / Q000503:physiopathology; D019910:Mycobacterium marinum / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D009171:Mycolic Acids / Q000737:chemistry* / Q000378:metabolism*; D010539:Permeability; D010588:Phagosomes / Q000378:metabolism / Q000382:microbiology; D012293:Rifampin / Q000494:pharmacology; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013055:Spectrophotometry, Infrared
chemical_list: D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D023082:Defensins; D009171:Mycolic Acids; D002569:Cerulenin; D012967:Sodium Dodecyl Sulfate; D009113:Muramidase; D012293:Rifampin