Published online 26 April 2004 doi:10.1084/jem.20031956
Rockefeller University Press, 0022-1007 $8.00
JEM, Volume 199, Number 9, 1191-1199
Arylamine N-Acetyltransferase Is Required for Synthesis of Mycolic Acids and Complex Lipids in Mycobacterium bovis BCG and Represents a Novel Drug Target
Sanjib Bhakta1,
Gurdyal S. Besra3,
Anna M. Upton1,
Tanya Parish5,
Carolyn Sholto-Douglas-Vernon1,
Kevin J.C. Gibson3,
Stuart Knutton4,
Siamon Gordon2,
Rosangela P. daSilva2,
Matthew C. Anderton1, and
Edith Sim1
1 Department of Pharmacology and 2 Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
3 Department of Biosciences and 4 Institute of Child Health, University of Birmingham, Birmingham B4 6NH, UK
5 Department of Medical Microbiology, Barts and the London, Queen Mary's School of Medicine and Dentistry, London E1 2AD, UK
Address correspondence to Edith Sim, Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK. Phone: 44-1865-271883; Fax: 44-1865-271853; email: edith.sim{at}pharm.ox.ac.uk
Mycolic acids represent a major component of the unique cell wall of mycobacteria. Mycolic acid biosynthesis is inhibited by isoniazid, a key frontline antitubercular drug that is inactivated by mycobacterial and human arylamine N-acetyltransferase (NAT). We show that an in-frame deletion of Mycobacterium bovis BCG nat results in delayed entry into log phase, altered morphology, altered cell wall lipid composition, and increased intracellular killing by macrophages. In particular, deletion of nat perturbs biosynthesis of mycolic acids and their derivatives and increases susceptibility of M. bovis BCG to antibiotics that permeate the cell wall. Phenotypic traits are fully complemented by introduction of Mycobacterium tuberculosis nat. We infer from our findings that NAT is critical to normal mycolic acid synthesis and hence other derivative cell wall components and represents a novel target for antituberculosis therapy. In addition, this is the first report of an endogenous role for NAT in mycobacteria.
Key Words: isoniazid macrophage Mycobacterium tuberculosis cell wall metabolism
A. Upton's present address is The Rockefeller University, 1230 York Avenue, New York, NY 10021.
Abbreviations used in this paper: ADC, albumin-dextrose-catalase; CF, cord factor; GMM, glucose monomycolate; INH, isoniazid; MK, menaquinone; NAT, arylamine N-acetyltransferase; OADC, oleic acidADC; ORF, open reading frame; PDIM, phthiocerol dimycocerosate; SEM, scanning electron microscopy; TEM, transmission electron microscopy; TLC, thin layer chromatography.

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