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.
Bishop
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Department of Biochemistry, Duke University Medical Center, 255 Nanaline Duke Building, Box 3711, Durham, NC 27710, USA.
Gibbons
H S
HS
Guina
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Trent
M S
MS
Miller
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SI
Raetz
C R
CR
D000215:Acylation; D000217:Acyltransferases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D002240:Carbohydrate Sequence; D002462:Cell Membrane; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D008050:Lipid A / Q000096:biosynthesis / Q000378:metabolism*; D008969:Molecular Sequence Data; D010168:Palmitates / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008050:Lipid A; D010168:Palmitates; C079792:PhoQ protein, Bacteria; D010743:Phospholipids; D000217:Acyltransferases