Mycobacterium tuberculosis possesses unique cell-surface lipids that have been implicated in virulence. One of the most abundant is sulfolipid-1 (SL-1), a tetraacyl-sulfotrehalose glycolipid. Although the early steps in SL-1 biosynthesis are known, the machinery underlying the final acylation reactions is not understood. We provide genetic and biochemical evidence for the activities of two proteins, Chp1 and Sap (corresponding to gene loci rv3822 and rv3821), that complete this pathway. The membrane-associated acyltransferase Chp1 accepts a synthetic diacyl sulfolipid and transfers an acyl group regioselectively from one donor substrate molecule to a second acceptor molecule in two successive reactions to yield a tetraacylated product. Chp1 is fully active in vitro, but in M. tuberculosis, its function is potentiated by the previously identified sulfolipid transporter MmpL8. We also show that the integral membrane protein Sap and MmpL8 are both essential for sulfolipid transport. Finally, the lipase inhibitor tetrahydrolipstatin disrupts Chp1 activity in M. tuberculosis, suggesting an avenue for perturbing SL-1 biosynthesis in vivo. These data complete the SL-1 biosynthetic pathway and corroborate a model in which lipid biosynthesis and transmembrane transport are coupled at the membrane-cytosol interface through the activity of multiple proteins, possibly as a macromolecular complex.
biosynthesis, Mycobacterium tuberculosis, sulfolipid, SL-1
NCBI PubMed ID: 22194604Publication DOI: 10.1074/jbc.M111.315473Journal NLM ID: 2985121RPublisher: Baltimore, MD: American Society for Biochemistry and Molecular Biology
Correspondence: Bertozzi CR
Institutions: Department of Chemistry, University of California, Berkeley, USA, Department of Molecular and Cell Biology, University of California, Berkeley, USA, Howard Hughes Medical Institute, University of California, Berkeley, USA, Department of Molecular and Cellular Biology, University of California, Davis, USA, Department of Chemical Physiology, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, USA, Department of Microbiology, University of Alabama at Birmingham, Birmingham, USA
Methods: DNA techniques, extraction, isotopic labeling, cell growth, enzymatic assay, centrifugation, FTICR-MS
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