Lipid A substitution profiles of meningococcal oxidoreductase mutants.

<p>Lipid A profiles of LOS extracted from <i>N. meningitidis</i> strain NMB (Panel A), NMBΔ<i>lptA::aadA</i> (Panel B), NMBΔ<i>NmdsbA1</i>/<i>NmdsbA2</i> (Panel C), NMBΔ<i>NmdsbA3</i> (Panel D) and NMBΔ<i>dsbA1/dsbA2/dsbA3</i> (Panel E) as determined by MALDI-TOF MS. <i>bis</i>-Phosphorylated hexaacylated lipid A (<i>m/z</i> = 1712), the <i>mono</i>-phosphorylated (<i>m/z</i> = 1632) and the <i>tri</i>-phosphorylated derivative (<i>m/z</i> = 1792) were detected in all strains. Strain NMB and the oxidoreductase mutants all expressed the mono-phosphorylated, <i>bis</i>-phosphorylated and <i>tri</i>-phosphorylated hexaacylated lipid A with a single PEA addition (<i>m/z</i> = 1755, <i>m/z</i> = 1835 and <i>m/z</i> = 1915). Consistent with the loss of LptA activity, NMBΔ<i>lptA::aadA</i> lacked these ions.