Open AccessCrystal structure and catalytic mechanism of the LPS 3-O-deacylase PagL fromPseudomonas aeruginosa
Author(s) -
Lucy Rutten,
Jeroen Geurtsen,
Wietske Lambert,
Jeroen J. M. Smolenaers,
Alexandre M. J. J. Bonvin,
Alex de Haan,
Peter van der Ley,
Maarten R. Egmond,
Piet Gros,
Jan Tommassen
Publication year - 2006
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0509392103
Subject(s) - active site , bacterial outer membrane , lipid a , catalytic triad , lipid bilayer , chemistry , periplasmic space , stereochemistry , protein structure , residue (chemistry) , lipopolysaccharide , biochemistry , biophysics , biology , enzyme , membrane , escherichia coli , gene , endocrinology
Pathogenic Gram-negative bacteria can modify the lipid A portion of their lipopolysaccharide in response to environmental stimuli. 3-O -deacylation of lipid A by the outer membrane enzyme PagL modulates signaling through Toll-like receptor 4, leading to a reduced host immune response. We found that PagL is widely disseminated among Gram-negative bacteria. Only four residues are conserved: a Ser, His, Phe, and Asn residue. Here, we describe the crystal structure of PagL fromPseudomonas aeruginosa to 2.0-Å resolution. It consists of an eight-stranded β-barrel with the axis tilted by ≈30° with respect to the lipid bilayer. The structure reveals that PagL contains an active site with a Ser-His-Glu catalytic triad and an oxyanion hole that comprises the conserved Asn. The importance of active site residues was confirmed in mutagenesis studies. Although PagL is most likely active as a monomer, its active site architecture shows high resemblance to that of the dimeric 12-stranded outer membrane phospholipase A. Modeling of the substrate lipid X onto the active site reveals that the 3-O -acyl chain is accommodated in a hydrophobic groove perpendicular to the membrane plane. In addition, an aspartate makes a hydrogen bond with the hydroxyl group of the 3-O -acyl chain, probably providing specificity of PagL toward lipid A.