The structure was elucidated in this paper NCBI PubMed ID:20795687 Journal NLM ID:0370623 Publisher: American Chemical Society Correspondence: raetzbiochem.duke.edu Institutions: Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA
The lipid A moiety of Escherichia coli lipopolysaccharide is a hexaacylated disaccharide of glucosamine that is phosphorylated at the 1 and 4' positions. Expression of the Francisella novicida lipid A 1-phosphatase FnLpxE in E. coli results in dephosphorylation of the lipid A proximal unit. Coexpression of FnLpxE and the Rhizobium leguminosarum lipid A oxidase RlLpxQ in E. coli converts much of the proximal glucosamine to 2-amino-2-deoxygluconate. Expression of the F. novicida lipid A 4'-phosphatase FnLpxF in wild-type E. coli has no effect because FnLpxF cannot dephosphorylate hexaacylated lipid A. However, expression of FnLpxF in E. coli lpxM mutants, which synthesize pentaacylated lipid A lacking the secondary 3'-myristate chain, causes extensive 4'-dephosphorylation. Coexpression of FnLpxE and FnLpxF in lpxM mutants results in massive accumulation of lipid A species lacking both phosphate groups, and introduction of RlLpxQ generates phosphate-free lipid A variants containing 2-amino-2-deoxygluconate. The proposed lipid A structures were confirmed by electrospray ionization mass spectrometry. Strains with 4'-dephosphorylated lipid A display increased polymyxin resistance. Heptose-deficient mutants of E. coli lacking both the 1- and 4'-phosphate moieties are viable on plates but sensitive to CaCl(2). Our methods for reengineering lipid A structure may be useful for generating novel vaccines and adjuvants.
lipopolysaccharides, Escherichia coli, Rhizobia, mass spectrometry, lipid A structure, polymyxin
Methods: DNA techniques, ESI-MS, mild acid hydrolysis, genetic methods, enzymatic modification Enzymes that release or process the structure: LpxE,LpxF,LpxQ Comments, role: lipid A of mutant strain E. coli SR8209/pWSK29-LpxQEF LPS
Related record ID(s): 31140, 31185, 31186, 31187, 31188, 31189, 31190, 31191, 31192, 31193, 31195, 31196 NCBI Taxonomy refs (TaxIDs):562 Show glycosyltransferases
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