Decoding the roles of pilotins and accessory proteins in secretin escort services

Authors

  • Jason Koo,

    1. Program in Molecular Structure and Function, The Hospital for Sick Children, Toronto, ON, Canada
    2. Department of Biochemistry, University of Toronto, Toronto, ON, Canada
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  • Lori L. Burrows,

    Corresponding author
    1. Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
    • Program in Molecular Structure and Function, The Hospital for Sick Children, Toronto, ON, Canada
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  • P. Lynne Howell

    Corresponding author
    1. Department of Biochemistry, University of Toronto, Toronto, ON, Canada
    • Program in Molecular Structure and Function, The Hospital for Sick Children, Toronto, ON, Canada
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Correspondence: Lori L. Burrows, 4H18 Health Sciences Centre, 1200 Main St. West, Hamilton, ON L8N3Z5, Canada. Tel.: +1 905 525 9140; fax: +1 905 522 9033; e-mail: burrowl@mcmaster.ca

P. Lynne Howell, Room 3507A, The Hospital for Sick Children, 555 University Ave., Toronto, ON M5G1X8, Canada. Tel.: +1 416 813 5378; fax: +1 416 813 5379; e-mail: howell@sickkids.ca

Abstract

Secretins are channels that allow translocation of macromolecules across the outer membranes of Gram-negative bacteria. Virulence, natural competence, and motility are among the functions mediated by these large oligomeric protein assemblies. Filamentous phage also uses secretins to exit their bacterial host without causing cell lysis. However, the secretin is only a part of a larger membrane-spanning complex, and additional proteins are often required for its formation. A class of outer membrane lipoproteins called pilotins has been implicated in secretin assembly and/or localization. Additional accessory proteins may also be involved in secretin stability. Significant progress has recently been made toward deciphering the complex interactions required for functional secretin assembly. To allow for easier comparison between different systems, we have classified the secretins into five different classes based on their requirements for proteins involved in their assembly, localization, and stability. An overview of pilotin and accessory protein structures, functions, and characterized modes of interaction with the secretin is presented.

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