Cryo-em reveals new species-specific proteins and symmetry elements in the legionella pneumophila dot/icm t4ss

Michael J. Sheedlo, Clarissa L. Durie, Jeong Min Chung, Louise Chang, Jacquelyn Roberts, Michele Swanson, Dana Borden Lacy, Melanie D. Ohi

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Legionella pneumophila is an opportunistic pathogen that causes the potentially fatal pneumonia known as Legionnaires’ disease. The pathology associated with infection depends on bacterial delivery of effector proteins into the host via the membrane spanning Dot/Icm type IV secretion system (T4SS). We have determined sub-3.0 Å resolution maps of the Dot/Icm T4SS core complex by single particle cryo-EM. The high-resolution structural analysis has allowed us to identify proteins encoded outside the Dot/Icm genetic locus that contribute to the core T4SS structure. We can also now define two distinct areas of symmetry mismatch, one that connects the C18 periplasmic ring (PR) and the C13 outer membrane cap (OMC) and one that connects the C13 OMC with a 16-fold symmetric dome. Unexpectedly, the connection between the PR and OMC is DotH, with five copies sandwiched between the OMC and PR to accommodate the symmetry mismatch. Finally, we observe multiple conformations in the reconstructions that indicate flexibility within the structure.

Original languageEnglish (US)
Article numbere70427
StatePublished - Sep 2021

Bibliographical note

Funding Information:
The work described here was supported by NIH R01AI118932 (MDO), and R21AI6465 (MS and MDO), F32 AI150027-01 (CLD), NIH T32DK007673 (MJS), K99AI154672 (MJS), S10OD020011, S10OD030275, the National Science Foundation DGE1841052 (JR) and the University of Michigan Department of Microbiology and Immunology (Swanson). Some of this work was performed at the Stanford-SLAC Cryo-EM Facilities, supported by Stanford University, SLAC, and the National Institutes of Health S10 Instrumentation Programs. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The molecular graphics and analyses presented here were performed with UCSF Chimera (developed by the Resource for Biocomputing, Visualization, and Informatics at UC-San Francisco, with support from NIH P41-GM103311) and ChimeraX (developed by the Resource for Biocomputing, Visualization, and Informatics at the University of California, San Francisco, with support from National Institutes of Health R01-GM129325 and the Office of Cyber Infrastructure and Computational Biology, National Institute of Allergy and Infectious Diseases). Mass spectrometry experiments were performed by the University of Michigan Proteomics Resource Facility. We thank T Knight for Legionella culture advice. We acknowledge the use of the U-M LSI cryo-EM facility, managed by M Su, A Bondy, and L Koepping, and U-M LSI IT support. We thank U-M BSI and LSI for significant support of the cryo-EM facility.

Publisher Copyright:
‍© Sheedlo et al.


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