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  • The EMBO Journal (2006) 25, 2652 - 2661
  • doi:10.1038/sj.emboj.7601130

Published online: 11 May 2006

Cytotoxin ClyA from Escherichia coli assembles to a 13-meric pore independent of its redox-state

Nora Eifler1,a, Michael Vetsch2,ab, Marco Gregorini1, Philippe Ringler1, Mohamed Chami1, Ansgar Philippsen1, Andrea Fritz2, Shirley A Müller1, Rudi Glockshuber2, Andreas Engel1 and Ulla Grauschopf2

  1. Maurice E Müller Institute for Microscopy, Biozentrum, University of Basel, Basel, Switzerland
  2. Institute for Molecular Biology & Biophysics, ETH Zürich, Zürich, Switzerland

Correspondence to:

Andreas Engel, Maurice E Müller Institute for Microscopy, Bonzentrum, University of Basel, 4056 Basel, Switzerland. Tel.: +41 61 267 22 61; Fax: +41 61 267 21 09; E-mail: andreas.engel@unibas.ch

Ulla Grauschopf, Institute for Molecular Biology & Biophysics, ETH Zürich, 8093 Zürich, Switzerland. Tel.: +41 44 633 24 82; Fax: +41 44 633 10 36; E-mail: ulla.grauschopf@mol.biol.ethz.ch

aThese authors contributed equally to this work

bPresent address: Novartis Pharma AG, 4002 Basel, Switzerland

Received 15 December 2005; Accepted 13 April 2006

ClyA is a pore-forming toxin from virulent Escherichia coli and Salmonella enterica strains. Here, we show that the intrinsic hemolytic activity of ClyA is independent of its redox state, and that the assembly of both reduced and oxidized ClyA to the ring-shaped oligomer is triggered by contact with lipid or detergent. A rate-limiting conformational transition in membrane-bound ClyA monomers precedes their assembly to the functional pore. We obtained a three-dimensional model of the detergent-induced oligomeric complex at 12 Å resolution by combining cryo- and negative stain electron microscopy with mass measurements by scanning transmission electron microscopy. The model reveals that 13 ClyA monomers assemble into a cylinder with a hydrophobic cap region, which may be critical for membrane insertion.

  • Keywords:

    • assembly,
    • electron microscopy,
    • pore-forming toxin,
    • structure