title: Structure of the Pseudomonas aeruginosa Type IVa Pilus Secretin at 7.4 Å.
abstract: Type IVa pili (T4aP) function as bacterial virulence factors. T4aP pass through the outer membranes of Gram-negative bacteria via homo-oligomeric secretins. We present a 7.4 Å cryoelectron microscopy structure of the Pseudomonas aeruginosa PilQ secretin. Peripheral and internal features show that the secretin is composed of 14 subunits with C7 symmetry. The channel is a ribbed cylinder with central peripheral spokes and a central gate closed on the periplasmic side. The structure suggests that during pilus extrusion, the central gate is displaced to the interior walls and that no additional conformational changes are required, as the internal diameter can accommodate the pilus. The N1 domain was resolved, while the N0 and the N-terminal β-domains proposed to bind peptidoglycan were absent in class average images and the final 3D map, indicating a high flexibility. These data provide the highest-resolution structure to date of a T4aP secretin.
authors.affiliation: Program in Molecular Structure and Function, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, 1 Kings Circle, Toronto ON M5S 1A8, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Koo
authors.affiliation: Department of Biochemistry and Biomedical Sciences and the Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, 1280 Main St W., Hamilton, ON L8S 4K1, Canada.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Lamers
authors.affiliation: Program in Molecular Structure and Function, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, 1 Kings Circle, Toronto ON M5S 1A8, Canada; Department of Medical Biophysics, University of Toronto, 101 College Street, Toronto, ON M5G 1l7, Canada. Electronic address: john.rubinstein@utoronto.ca.
authors.forename: John L
authors.initials: JL
authors.lastname: Rubinstein
authors.affiliation: Department of Biochemistry and Biomedical Sciences and the Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, 1280 Main St W., Hamilton, ON L8S 4K1, Canada. Electronic address: burrowl@mcmaster.ca.
authors.forename: Lori L
authors.initials: LL
authors.lastname: Burrows
authors.affiliation: Program in Molecular Structure and Function, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, 1 Kings Circle, Toronto ON M5S 1A8, Canada. Electronic address: howell@sickkids.ca.
authors.forename: P Lynne
authors.initials: PL
authors.lastname: Howell
mesh_terms: D020285:Cryoelectron Microscopy; D036781:Fimbriae Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D010457:Peptidoglycan / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010457:Peptidoglycan; C084295:pilQ protein, bacteria; D036781:Fimbriae Proteins