Transfer of palmitate from phospholipids to lipid A in outer membranes of gram-negative bacteria.
Regulated covalent modifications of lipid A are implicated in virulence of pathogenic Gram-negative bacteria. The Salmonella typhimurium PhoP/PhoQ- activated gene pagP is required both for biosynthesis of hepta-acylated lipid A species containing palmitate and for resistance to cationic anti-microbial peptides. Palmitoylated lipid A can also function as an endotoxin antagonist. We now show that pagP and its Escherichia coli homolog (crcA) encode an unusual enzyme of lipid A biosynthesis localized in the outer membrane. PagP transfers a palmitate residue from the sn-1 position of a phospholipid to the N-linked hydroxymyristate on the proximal unit of lipid A (or its precursors). PagP bearing a C-terminal His(6)-tag accumulated in outer membranes during overproduction, was purified with full activity and was shown by cross-linking to behave as a homodimer. PagP is the first example of an outer membrane enzyme involved in lipid A biosynthesis. Additional pagP homologs are encoded in the genomes of YERSINIA: and BORDETELLA: species. PagP may provide an adaptive response toward both Mg(2+) limitation and host innate immune defenses.[1]References
- Transfer of palmitate from phospholipids to lipid A in outer membranes of gram-negative bacteria. Bishop, R.E., Gibbons, H.S., Guina, T., Trent, M.S., Miller, S.I., Raetz, C.R. EMBO J. (2000) [Pubmed]
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