9NH2

In situ cryo-EM structure of porin III of the Legionella Dot/Icm T4SS machine

This is a non-PDB format compatible entry.

Summary for 9NH2

• Entry DOI: 10.2210/pdb9nh2/pdb
• EMDB information: 49395
• Descriptor: Outer membrane protein beta-barrel domain-containing protein (1 entity in total)
• Functional Keywords: type ivb dot/icm secretion machine, protein transport
• Biological source: Legionella pneumophila subsp. pneumophila
• Total number of polymer chains: 16
• Total formula weight: 421832.59

Authors

Yue, J.,Liu, J. (deposition date: 2025-02-23, release date: 2025-09-17)

Primary citation

Yue, J.,Heydari, S.,Park, D.,Chetrit, D.,Tachiyama, S.,Guo, W.,Botting, J.M.,Wu, S.,Roy, C.R.,Liu, J.
In-situ structures of the Legionella Dot/Icm T4SS identify the DotA-IcmX complex as the gatekeeper for effector translocation.
Biorxiv, 2025

PubMed Abstract: The Dot/Icm machine in is one of the most versatile type IV secretion systems (T4SSs), with a remarkable capacity to translocate over 330 different effector proteins across the bacterial envelope into host cells. At least 27 Dot and Icm proteins are required for assembly and function of the system, yet the architecture and activation mechanism remain poorly understood at the molecular level. Here, we deploy cryo-electron microscopy to reveal structures of the Dot/Icm machine at near-atomic resolution. Importantly, two proteins essential for effector translocation, DotA and IcmX, form a pentameric protochannel at an inactive state. Upon activation, the DotA-IcmX protochannel undergoes extensive rearrangements to form an extended transenvelope passage capable of transporting effector proteins from the bacterial cytoplasm into host cells as revealed by cryo-electron tomography. Collectively, our findings suggest that the DotA-IcmX complex functions as the gatekeeper for effector translocation of the Dot/Icm T4SS.

PubMed: 40666918
DOI: 10.1101/2025.06.23.660953

Experimental method

ELECTRON MICROSCOPY (4.05 Å)