Bordetella parapertussis PagP Mediates the Addition of Two Palmitates to the Lipopolysaccharide Lipid A

Bordetella bronchiseptica PagP (PagP(BB)) is a lipid A palmitoyl transferase that is required for resistance to antibody-dependent complement-mediated killing in a murine model of infection. B. parapertussis contains a putative pagP homolog (encoding B. parapertussis PagP [PagP(BPa)]), but its role in the biosynthesis of lipid A, the membrane anchor of lipopolysaccharide (LPS), has not been investigated. Mass spectrometry analysis revealed that wild-type B. parapertussis lipid A consists of a heterogeneous mixture of lipid A structures, with penta-and hexa-acylated structures containing one and two palmitates, respectively. Through mutational analysis, we demonstrate that PagP(BPa) is required for the modification of lipid A with palmitate. While PagP(BB) transfers a single palmitate to the lipid A C-3' position, PagP(BPa) transfers palmitates to the lipid A C-2 and C-3' positions. The addition of two palmitate acyl chains is unique to B. parapertussis. Mutation of pagP(BPa) resulted in a mutant strain with increased sensitivity to antimicrobial peptide killing and decreased endotoxicity, as evidenced by reduced proinflammatory responses via Toll-like receptor 4 (TLR4) to the hypoacylated LPS. Therefore, PagP-mediated modification of lipid A regulates outer membrane function and may be a means to modify interactions between the bacterium and its human host during infection.