Analysis of lipid A structure in Escherichia coli mutant strains by MALDI-TOF Mass Spectrometry

Lipid A structure of Escherichia coli mutants constructed by insertional mutation of myristoyltransferase(MSBB) gene and reintroduction of the gene were analyzed by Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry(MALDI-TOF MS). Lipid A samples were prepared by mild-acid hydrolysis of lipopolysaccharides extracted from E. coli strains. Compared to the wild-type strain, the MSBB-knockout strain produced the lipid A lacking myristic acid, and that change was recovered by introducing the plasmid-encoded MSBB gene. The structural difference of these lipid A preparations, and the presence of several molecular species of lipid A containing different number of fatty acids were clearly detected by MALDI-TOF MS. These results indicated that MALDI-TOF MS is a powerful method for the structural analysis of lipid A as well as other glycolipids or phospholipids