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. 2004 Jan;186(2):575–579. doi: 10.1128/JB.186.2.575-579.2004

FIG. 2.

FIG. 2.

Association of pmrB mutations with constitutive addition of aminoarabinose to P. aeruginosa lipid A. (A) MALDI-TOF negative-ion mode analysis of lipid A purified from P. aeruginosa strain PAK. In the negative-ion mode, observed molecular species lack at least one proton: [M—H]−. The difference between [M—H]− at m/z 1,447 and m/z 1,617 (Δm/z = 170) in the mass spectrum indicates the loss of 3-hydroxydecanoate from position 3 of the reducing diglucosamine (right-hand ring in panel C). (B) Mass spectrum for lipid A from strain PAKpmrB6. The difference between [M—H]− at m/z 1,617, 1,748, and 1,879 (Δm/z = 131) indicates the addition of aminoarabinose to the 1 and 4′ phosphates of lipid A. (C) Structure of P. aeruginosa lipid A without and with aminoarabinose. The X− symbol at the right side of the lower structure represents either H (corresponding to m/z 1,748) or aminoarabinose (corresponding to m/z 1,879). The fatty acids depicted are 3-hydroxydecanoate (3-OH C10:0), laurate (C12:0), 2-hydroxylaurate (2-OH C12:0), and 3-hydroxylaurate (3-OH C12:0).