FIG. 6.

Complementation of lptA::spc restores 4-PEA substitution of lipid A. Lipid A was purified from complemented strain FA19 lptA::spc lptA⁺ grown in the absence (A) or presence (B) of 1 mM IPTG. Shown are the MALDI-TOF MS spectra for the lipid A species. Note that for the lipid A prepared from gonococci grown in the presence of IPTG, the levels of the two major PEA-containing species, with [M-H]⁻ ions of m/z 1,836.72 and 1,756.66, are elevated compared to the species in the same strain grown in the absence of IPTG. The single-digit numbers above ion peaks refer to structures shown in Fig. 5B.