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. 2009 Jul 17;284(38):25804–25812. doi: 10.1074/jbc.M109.022772

FIGURE 6.

FIGURE 6.

MALDI-TOF mass spectrometry confirms Vc0213 is the E. coli LpxL homolog. Lipid A of E. coli MKV13 (lpxL and lpxP) expressing pBluescript (A) or pBSVc0213 (B) were analyzed by MALDI-TOF mass spectrometry in the negative ion mode. The major ion peak in A is m/z 1404.5 amu, which corresponds to the expected mass of lipid IVA. The major peak in B is m/z 1824.6 amu, indicating that Vc0213 is adding a myristate (C14:0) to the 2′-position of the glucosamine disaccharide. Endogenous MKV13 LpxM adds a C14:0 to the 3′-position, thus producing the hexa-acylated lipid A species with a predicted mass of 1825.3 (inset structure). Minor peaks are explained below: at 1614.5 amu, the addition of a single C14:0; at 1324.6 amu, the loss of phosphate group at 1-position of the glucosamine disaccharide from parent ion; and at 1426.6 amu, the addition of a sodium adduct.