Architecture of the Vibrio cholerae toxin-coregulated pilus machine revealed by electron cryotomography
Abstract
Type IV pili (T4P) are filamentous appendages found on many Bacteria and Archaea. They are helical fibres of pilin proteins assembled by a multi-component macromolecular machine we call the basal body. Based on pilin features, T4P are classified into type IVa pili (T4aP) and type IVb pili (T4bP). T4aP are more widespread and are involved in cell motility, DNA transfer, host predation and electron transfer. T4bP are less prevalent and are mainly found in enteropathogenic bacteria, where they play key roles in host colonization. Following similar work on T4aP machines, here we use electron cryotomography to reveal the three-dimensional in situ structure of a T4bP machine in its piliated and non-piliated states. The specific machine we analyse is the Vibrio cholerae toxin-coregulated pilus machine (TCPM). Although only about half of the components of the TCPM show sequence homology to components of the previously analysed Myxococcus xanthus T4aP machine (T4aPM), we find that their structures are nevertheless remarkably similar. Based on homologies with components of the M. xanthus T4aPM and additional reconstructions of TCPM mutants in which the non-homologous proteins are individually deleted, we propose locations for all eight TCPM components within the complex. Non-homologous proteins in the T4aPM and TCPM are found to form similar structures, suggesting new hypotheses for their functions and evolutionary histories.
Additional Information
© 2017 Macmillan Publishers Limited. Received: 16 May 2016; Accepted: 14 December 2016; Published online: 06 February 2017. The authors thank C. Oikonomou and C. Shaffer for discussions and editorial assistance. This work was supported by NIH grant R01 AI127401 to G.J.J., the Howard Hughes Medical Institute and the John Templeton Foundation as part of the Boundaries of Life project. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. Data availability: The sub-tomogram averages of TCPMs that support the findings of this study have been deposited in the Electron Microscopy Data Bank under the following accession codes: EMD-8492 (wild-type, non-piliated, aligned on the OM part); EMD-8493 (wild-type, non-piliated, aligned on the IM part); EMD-8494 (wild-type, piliated, aligned on the OM part); EMD-8495 (wild-type, piliated, aligned on the IM part); EMD-8496 (ΔtcpS, non-piliated, aligned on the OM part); EMD-8497 (ΔtcpS, non-piliated, aligned on the IM part); EMD-8498 (ΔtcpB, non-piliated, aligned on the OM part); EMD-8499 (ΔtcpB, non-piliated, aligned on the IM part); EMD-8500 (ΔtcpD, non-piliated, aligned on the OM part); EMD-8501 (ΔtcpD, non-piliated, aligned on the IM part); EMD-8502 (ΔtcpR, non-piliated, aligned on the OM part); and EMD-8503 (ΔtcpR, non-piliated, aligned on the IM part). Author Contributions: Y.-W.C. and A.K. collected, processed and analysed the ECT data. D.R.O. performed the bioinformatics analyses. L.A.R. assisted with ECT data processing. G.K., J.A.S. and R.K.T. provided the V. cholerae strains. Y.-W.C., A.K., D.R.O. and G.J.J. wrote the paper. The authors declare no competing financial interests.Attached Files
Accepted Version - nihms836833.pdf
Supplemental Material - nmicrobiol2016269-s1.pdf
Supplemental Material - nmicrobiol2016269-s2.mov
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Additional details
- PMCID
- PMC5302817
- Eprint ID
- 72611
- Resolver ID
- CaltechAUTHORS:20161206-161836906
- R01 AI127401
- NIH
- Howard Hughes Medical Institute (HHMI)
- John Templeton Foundation
- Created
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2017-02-09Created from EPrint's datestamp field
- Updated
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2022-04-05Created from EPrint's last_modified field