title: A divergent Pseudomonas aeruginosa palmitoyltransferase essential for cystic fibrosis-specific lipid A.
abstract: 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.
authors.affiliation: Department of Microbial Pathogenesis, University of Maryland, School of Dentistry, University of Maryland, Baltimore, MD, 21201, USA; Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Prannok Road, Bangkoknoi, Bangkok, 10700, Thailand.
authors.forename: Iyarit
authors.initials: I
authors.lastname: Thaipisuttikul
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Hittle
authors.forename: Ramesh
authors.initials: R
authors.lastname: Chandra
authors.forename: Daniel
authors.initials: D
authors.lastname: Zangari
authors.forename: Charneal L
authors.initials: CL
authors.lastname: Dixon
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Garrett
authors.forename: David A
authors.initials: DA
authors.lastname: Rasko
authors.forename: Nandini
authors.initials: N
authors.lastname: Dasgupta
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Moskowitz
authors.forename: Lars
authors.initials: L
authors.lastname: Malmström
authors.forename: David R
authors.initials: DR
authors.lastname: Goodlett
authors.forename: Samuel I
authors.initials: SI
authors.lastname: Miller
authors.forename: Russell E
authors.initials: RE
authors.lastname: Bishop
authors.forename: Robert K
authors.initials: RK
authors.lastname: Ernst
mesh_terms: D020384:Acidic Glycosphingolipids; D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D023181:Antimicrobial Cationic Peptides / Q000276:immunology / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020134:Catalytic Domain; D003550:Cystic Fibrosis / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D016207:Cytokines / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate; D008050:Lipid A / Q000276:immunology / Q000378:metabolism*; D054878:Lipoylation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010168:Palmitates / Q000378:metabolism*; D010802:Phylogeny; D011112:Polymyxin B / Q000494:pharmacology; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000187:drug effects / Q000276:immunology / Q000378:metabolism
chemical_list: D020384:Acidic Glycosphingolipids; D023181:Antimicrobial Cationic Peptides; D001426:Bacterial Proteins; D016207:Cytokines; D029968:Escherichia coli Proteins; D008050:Lipid A; C037242:Lipid IV; D010168:Palmitates; D000217:Acyltransferases; C468520:PagP protein, E coli; D011112:Polymyxin B