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  • The EMBO Journal (2007) 26, 2594 - 2604
  • doi:10.1038/sj.emboj.7601693

Published online: 26 April 2007

Structure of colicin I receptor bound to the R-domain of colicin Ia: implications for protein import

Susan K Buchanan1, Petra Lukacik1, Sylvestre Grizot1,a, Rodolfo Ghirlando1, Maruf MU Ali1,b, Travis J Barnard1, Karen S Jakes2, Paul K Kienker2 and Lothar Esser3

  1. Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
  2. Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY, USA
  3. Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA

Correspondence to:

Susan K Buchanan, Laboratory of Molecular Biology, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, 50 South Drive, Room 4503, Bethesda, MD 20892, USA. Tel.: +1 301 594 9222; Fax: +1 301 480 0597; E-mail: skbuchan@helix.nih.gov

aPresent address: Cellectis SA, 102 route de Noisy, F-93235 Romainville Cedex, France

bPresent address: Section of Structural Biology, Institute of Cancer Research, London SW3 6JB, UK

Received 21 December 2006; Accepted 29 March 2007

Colicin Ia is a 69 kDa protein that kills susceptible Escherichia coli cells by binding to a specific receptor in the outer membrane, colicin I receptor (70 kDa), and subsequently translocating its channel forming domain across the periplasmic space, where it inserts into the inner membrane and forms a voltage-dependent ion channel. We determined crystal structures of colicin I receptor alone and in complex with the receptor binding domain of colicin Ia. The receptor undergoes large and unusual conformational changes upon colicin binding, opening at the cell surface and positioning the receptor binding domain of colicin Ia directly above it. We modelled the interaction with full-length colicin Ia to show that the channel forming domain is initially positioned 150 Å above the cell surface. Functional data using full-length colicin Ia show that colicin I receptor is necessary for cell surface binding, and suggest that the receptor participates in translocation of colicin Ia across the outer membrane.

  • Keywords:

    • active transport,
    • colicin,
    • outer membrane protein,
    • protein import,
    • TonB