The binding of cholera toxin to the periplasmic vestibule of the type II secretion channel

Steve L. Reichow, Konstantin V. Korotkov, Melissa Gonen, Ji Sun, Jaclyn R. Delarosa, Wim G.J. Hol, Tamir Gonen

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


The type II secretion system (T2SS) is a large macromolecular complex spanning the inner and outer membranes of many Gram-negative bacteria. The T2SS is responsible for the secretion of virulence factors such as cholera toxin (CT) and heat-labile enterotoxin (LT) from Vibrio cholerae and enterotoxigenic Escherichia coli, respectively. CT and LT are closely related AB5 heterohexamers, composed of one A sub-unit and a B-pentamer. Both CT and LT are translocated, as folded protein complexes, from the periplasm across the outer membrane through the type II secretion channel, the secretin GspD. We recently published the 19 Å structure of the V. cholerae secretin (VcGspD) in its closed state and showed by SPR measurements that the periplasmic domain of GspD interacts with the B-pentamer complex. Here we extend these studies by characterizing the binding of the cholera toxin B-pentamer to VcGspD using electron microscopy of negatively stained preparations. Our studies indicate that the pentamer is captured within the large periplasmic vestibule of VcGspD. These new results agree well with our previously published studies and are in accord with a piston-driven type II secretion mechanism.

Original languageEnglish
Pages (from-to)215-218
Number of pages4
Issue number3
StatePublished - 2011

Bibliographical note

Funding Information:
We thank the Murdock Charitable Trustand the Washington Research Foundationfor generous support of our electron cryomicroscopy laboratory. This research is supported by the National Institutes of Health grant AI34501. Tamir Gonen is a Howard Hughes Medical Institute Early Career Scientist. The authors declare no financial interest related to this work.


  • Cholera toxin
  • Electron cryomicroscopy
  • GspD
  • Secretin
  • Type II secretion system (T2SS)

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry


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