A divergent Pseudomonas aeruginosa palmitoyltransferase essential for cystic fibrosis‐specific lipid A

Abstract

Summary Strains of Pseudomonas aeruginosa (PA) isolated from the airways of cystic fibrosis patients constitutively add palmitate to lipid A, the membrane anchor of lipopolysaccharide. The PhoPQ regulated enzyme PagP is responsible for the transfer of palmitate from outer membrane phospholipids to lipid A. This enzyme had previously been identified in many pathogenic Gram-negative bacteria, but in PA had remained elusive, despite abundant evidence that its lipid A contains palmitate. Using a combined genetic and biochemical approach, we identified PA1343 as the PA gene encoding PagP. Although PA1343 lacks obvious primary structural similarity with known PagP enzymes, the β-barrel tertiary structure with an interior hydrocarbon ruler appears to be conserved. PA PagP transfers palmitate to the 3’ position of lipid A, in contrast to the 2 position seen with the enterobacterial PagP. Palmitoylated PA lipid A alters host innate immune responses, including increased resistance to some antimicrobial peptides and an elevated pro-inflammatory response, consistent with the synthesis of a hexa-acylated structure preferentially recognized by the TLR4/MD2 complex. Palmitoylation commonly confers resistance to cationic antimicrobial peptides, however, increased cytokine production resulting in inflammation is not seen with other palmitoylated lipid A, indicating a unique role for this modification in PA pathogenesis.

Mutant Alleles of lptD Increase the Permeability of Pseudomonas aeruginosa and Define Determinants of Intrinsic Resistance to Antibiotics

“…aeruginosa has long been known to palmitoylate its LPS, but only recently has a pagP homolog (PA1343) been identified in PAO1 and shown to function as a palmitoyltransferase (83). We constructed a ⌬pagP-null mutant and isolated the 32 P-radiolabeled lipid A component of LPS from this strain as well as from the lptD4213 and lptD208 mutants and the wild-type parent.…”

Extracellular zinc induces phosphoethanolamine addition to Pseudomonas aeruginosa lipid A via the ColRS two‐component system

“…In addition to these modifications, the toxicity of P. aeruginosa lipid A can be affected by altering the acylation pattern due to activity of the PagL deacylase or the PagP palmitoyl-transferase ( Fig. 1B; pink and green) (Ernst, 1999;Ernst et al, 2003;Thaipisuttikul et al, 2014). Aside from influencing endotoxicity, lipid A modifications can contribute to antimicrobial peptide resistance .…”

Lipid A structural modifications in extreme conditions and identification of unique modifying enzymes to define the Toll-like receptor 4 structure-activity relationship

“…PagP is a palmitoyltransferase that transfers a palmitate (C16:0) to the hydroxyl group of the 3-hydroxymyristate chain at position 2 (as examples Salmonella and E. coli ) or the 3’ position ( Pa ) resulting in a hepta- or hexa-acylated structure, respectively. [71,72] PagL[73] and LpxR[58] are 2 (as examples Salmonella and Pa ) and 3’ ( Hp, Salmonella , and Yersinia ) position deacylases, respectively. PagP and PagL are regulated by the two component regulatory system, PhoP/PhoQ, whereas LpxR is a Ca 2+ -dependent enzyme in Salmonella and temperature regulated in Yersinia .…”