BIOL 182 |
| The lipid A component of lipopolysaccharides from the plant endosymbionts Rhizobium etli and Rhizobium leguminosarum contains an unusual proximal sugar unit consisting of a 2-amino-2-deoxy-gluconate moiety in place of glucosamine. This modification results from the actions of the enzyme LpxQ, which generates the 2-amino-2-deoxy-gluconate unit from a glucosamine-containing precursor. LpxQ is localized to the outer membrane and is dependent on molecular oxygen for activity. LpxQ was shown to be active when expressed heterologously in E. coli. Lipid A was isolated from E. coli expressing LpxQ and was shown to be oxidized by ESI-mass spectrometry. A new substrate and assay were developed to monitor lipid A oxidation in vitro. LpxQ was shown to be inhibited by EDTA and not stimulated by FAD or PQQ. Hydrogen peroxide was not found to be a reaction product. A purification scheme was developed. The mechanism and cofactors involved in the oxidation reaction are under investigation. |
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Frontiers in Chemical Biology
5:00 PM-7:00 PM, Wednesday, August 22, 2007 BCEC -- Exhibit Hall - B2, Poster
Division of Biological Chemistry |