Molecular architecture of bacterial type IV secretion systems

Michael J. Sheedlo, Melanie D. Ohi, D. Borden Lacy, Timothy L. Cover

Research output: Contribution to journalReview articlepeer-review


Bacterial type IV secretion systems (T4SSs) are a versatile group of nanomachines that can horizontally transfer DNA through conjugation and deliver effector proteins into a wide range of target cells. The components of T4SSs in gram-negative bacteria are organized into several large subassemblies: an inner membrane complex, an outer membrane core complex, and, in some species, an extracellular pilus. Cryo-electron tomography has been used to define the structures of T4SSs in intact bacteria, and high-resolution structural models are now available for isolated core complexes from conjugation systems, the Xanthomonas citri T4SS, the Helicobacter pylori Cag T4SS, and the Legionella pneumophila Dot/Icm T4SS. In this review, we compare the molecular architectures of these T4SSs, focusing especially on the structures of core complexes. We discuss structural features that are shared by multiple T4SSs as well as evolutionary strategies used for T4SS diversification. Finally, we discuss how structural variations among T4SSs may confer specialized functional properties.

Original languageEnglish (US)
Article numbere1010720
Pages (from-to)e1010720
JournalPLoS pathogens
Issue number8
StatePublished - Aug 1 2022

Bibliographical note

Funding Information:
This work was supported by NIH AI118932 (TLC, MDO), CA116087 (TLC), AI039657 (TLC), AI164651 (MDO), and the Department of Veterans Affairs (I01BX004447) (TLC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Publisher Copyright:
This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

PubMed: MeSH publication types

  • Journal Article
  • Review
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, N.I.H., Extramural


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