FIGURE 4.
Δchp1 transports SL1278 to cell surface. Electrospray ionization Fourier transform ion cyclotron resonance MS analysis of lipid extracts from M. tuberculosis wild-type, Δsap, Δchp1, and ΔmmpL8 strains showed that the three knock-out strains lack SL-1 and accumulate SL1278. (To aid comparison, the m/z 2460 ion belonging to the SL-1 series is marked with a plus sign, and the m/z 1277.9, 1278.9, and 1279.9 ions belonging to the SL1278 series are marked with asterisks to distinguish them from other isobaric compounds in the lipid extracts). In addition, SL1278 was found in the surface lipid fraction only in Δchp1, and both SL-1 production and the SL1278 transport phenotype were restored by complementation with chp1.