Monophosphoryl lipid A (MLA) obtained from the lipopolysaccharide of Rhodopseudomonas sphaeroides ATCC 17023 was initially purified by silicic acid column chromatography to yield a single major pentaacyl MLA fraction. This fraction was methylated and further purified by reverse-phase high performance liquid chromtography to yield three prominent peak fractions. Laser desorption mass spectrometry of these three fractions allowed us to complete the important structural analysis of lipid A from this source. Three structurally distinct forms of dimethyl MLAwere identified where M(r) = 1447, 1449, and 1451 atomic mass units. These forms differed only by the presence or absence of unsaturation and keto group in the fatty acids. We established that the acyloxyacyl group (either Δ7-tetradecenoyloxytetradecanoate or tetradecanoyloxytetradecanoate) and the 3-ketotetradecanoate or hydroxytertadecanoate occupied the 2'- and 2-positions of the glucosamine disaccharide, respectively. Analysis of several minor fractions suggests that there is considerable structural heterogeneity in the MLA. With this new knowledge, the study of the structure-to-function relationship of the reported lack of toxicity of lipopolysaccharide from R. sphaeroides can be completed.
|Original language||English (US)|
|Number of pages||3|
|Journal||Journal of Biological Chemistry|
|State||Published - 1988|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology