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  • The EMBO Journal (2003) 22, 1969 - 1980
  • doi:10.1093/emboj/cdg223

VirB11 ATPases are dynamic hexameric assemblies: new insights into bacterial type IV secretion

Savvas N. Savvides1,2,7, Hye-Jeong Yeo1,3,7, Moriah R Beck1, Franca Blaesing4, Rudi Lurz4, Erich Lanka4, Renate Buhrdorf5, Wolfgang Fischer5, Rainer Haas5 and Gabriel Waksman1,3,6

  1. Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave, St Louis, MO 63110, USA
  2. Present address: Department of Ultrastructure, Vlaams Interuniversitair Instituut voor Biotechnologie, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
  3. School of Crystallography, Birkbeck College, Malet Street, London WC1E 7HX, UK
  4. Max Planck Institut für Molekulare Genetik, Ihnestrasse 73, Dahlem, D-14195 Berlin, Germany
  5. Max von Pettenkofer Institut, LMU Munich, Pettenkoferstrasse 9a, D-80336 Munich, Germany
  6. Department of Biochemistry and Molecular Biology, University College London, Gower Street London, WC1E 6BT, UK
  7. S.N.Savvides and H.-J.Yeo contributed equally to this work

Correspondence to:

Gabriel Waksman, E-mail: g.waksman@mail.cryst.bbk.ac.uk

Received 3 December 2002; Accepted 17 March 2003; Revised 3 February 2003

The coupling of ATP binding/hydrolysis to macromolecular secretion systems is crucial to the pathogenicity of Gram-negative bacteria. We reported previously the structure of the ADP-bound form of the hexameric traffic VirB11 ATPase of the Helicobacter pylori type IV secretion system (named HP0525), and proposed that it functions as a gating molecule at the inner membrane, cycling through closed and open forms regulated by ATP binding/hydrolysis. Here, we combine crystal structures with analytical ultracentrifugation experiments to show that VirB11 ATPases indeed function as dynamic hexameric assemblies. In the absence of nucleotide, the N-terminal domains exhibit a collection of rigid-body conformations. Nucleotide binding 'locks' the hexamer into a symmetric and compact structure. We propose that VirB11s use the mechanical leverage generated by such nucleotide-dependent conformational changes to facilitate the export of substrates or the assembly of the type IV secretion apparatus. Bio chemical characterization of mutant forms of HP0525 coupled with electron microscopy and in vivo assays support such hypothesis, and establish the relevance of VirB11s ATPases as drug targets against pathogenic bacteria.

  • Keywords:

    • bacterial pathogenesis,
    • crystal structure,
    • Helicobacter pylori,
    • HP0525,
    • VirB11 ATPases