title: The pilus usher controls protein interactions via domain masking and is functional as an oligomer.
abstract: The chaperone-usher (CU) pathway assembles organelles termed pili or fimbriae in Gram-negative bacteria. Type 1 pili expressed by uropathogenic Escherichia coli are prototypical structures assembled by the CU pathway. Biogenesis of pili by the CU pathway requires a periplasmic chaperone and an outer-membrane protein termed the usher (FimD). We show that the FimD C-terminal domains provide the high-affinity substrate-binding site but that these domains are masked in the resting usher. Domain masking requires the FimD plug domain, which serves as a switch controlling usher activation. We demonstrate that usher molecules can act in trans for pilus biogenesis, providing conclusive evidence for a functional usher oligomer. These results reveal mechanisms by which molecular machines such as the usher regulate and harness protein-protein interactions and suggest that ushers may interact in a cooperative manner during pilus assembly in bacteria.
authors.affiliation: 1] Center for Infectious Diseases, Stony Brook University, Stony Brook, New York, USA. [2] Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, USA.
authors.forename: Glenn T
authors.initials: GT
authors.lastname: Werneburg
authors.affiliation: 1] Center for Infectious Diseases, Stony Brook University, Stony Brook, New York, USA. [2] Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, USA.
authors.forename: Nadine S
authors.initials: NS
authors.lastname: Henderson
authors.affiliation: 1] Center for Infectious Diseases, Stony Brook University, Stony Brook, New York, USA. [2] Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, USA.
authors.forename: Erica B
authors.initials: EB
authors.lastname: Portnoy
authors.affiliation: 1] Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA. [2] Biosciences Department, Brookhaven National Laboratory, Upton, New York, USA.
authors.forename: Samema
authors.initials: S
authors.lastname: Sarowar
authors.affiliation: 1] Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, Missouri, USA. [2] Center for Women's Infectious Disease Research, Washington University School of Medicine, Saint Louis, Missouri, USA.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Hultgren
authors.affiliation: 1] Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA. [2] Biosciences Department, Brookhaven National Laboratory, Upton, New York, USA.
authors.forename: Huilin
authors.initials: H
authors.lastname: Li
authors.affiliation: 1] Center for Infectious Diseases, Stony Brook University, Stony Brook, New York, USA. [2] Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, USA.
authors.forename: David G
authors.initials: DG
authors.lastname: Thanassi
mesh_terms: D001665:Binding Sites; D004926:Escherichia coli / Q000737:chemistry / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D008958:Models, Molecular; D060066:Protein Interaction Maps; D017434:Protein Structure, Tertiary
chemical_list: D029968:Escherichia coli Proteins; C489283:fimD protein, E coli; D036781:Fimbriae Proteins