Crystal Structure of the Cystic Fibrosis Transmembrane Conductance Regulator Inhibitory Factor Cif Reveals Novel Active-Site Features of an Epoxide Hydrolase Virulence Factor

• DOI: 10.1128/jb.01348-09
• Publication Date: 2010-01-30T03:59:48Z
• Authors: Christopher D. Bahl; Christophe Morisseau; Jennifer M. Bombe...; Bruce A. Stanton; Bruce D. Hammock; George A. O'Toole; Dean R. Madden
• Keywords: Hydrolase; Virulence factor

Cystic fibrosis transmembrane conductance regulator (CFTR) inhibitory factor (Cif) is a virulence secreted by Pseudomonas aeruginosa that reduces the quantity of CFTR in apical membrane human airway epithelial cells. Initial sequence analysis suggested Cif an epoxide hydrolase (EH), but its violates two strictly conserved EH motifs and also compatible with other alpha/beta family members diverse substrate specificities. To investigate mechanistic basis activity, we have determined structure at 1.8-A resolution X-ray crystallography. The catalytic triad consists residues Asp129, His297, Glu153, which are across EHs. At positions, deviations from canonical active-site stereochemically conservative. Furthermore, detailed enzymatic confirms catalyzes hydrolysis compounds, specific activity against both epibromohydrin cis-stilbene oxide, relatively narrow range selectivity. Although closely related to classes structure, does not exhibit as either haloacetate dehalogenase or haloalkane dehalogenase. A reassessment structural functional consequences H269A mutation suggests Cif's effect on host-cell expression requires extended endogenous substrate.