Abstract
Legionella pneumophila is a bacterial pathogen that utilises a Type IV secretion (T4S) system to inject effector proteins into human macrophages. Essential to the recruitment and delivery of effectors to the T4S machinery is the membrane-embedded T4 coupling complex (T4CC). Here, we purify an intact T4CC from the Legionella membrane. It contains the DotL ATPase, the DotM and DotN proteins, the chaperone module IcmSW, and two previously uncharacterised proteins, DotY and DotZ. The atomic resolution structure reveals a DotLMNYZ hetero-pentameric core from which the flexible IcmSW module protrudes. Six of these hetero-pentameric complexes may assemble into a 1.6-MDa hexameric nanomachine, forming an inner membrane channel for effectors to pass through. Analysis of multiple cryo EM maps, further modelling and mutagenesis provide working models for the mechanism for binding and delivery of two essential classes of Legionella effectors, depending on IcmSW or DotM, respectively.
Highlights
Legionella pneumophila is a bacterial pathogen that utilises a Type IV secretion (T4S) system to inject effector proteins into human macrophages
We purified the T4 coupling complex (T4CC) from Legionella cell membranes after solubilisation with detergents and taking advantage of a Strep-tag inserted at the Cterminus of DotL (Methods and Supplementary Tables 1, 2 and 3)
The complex contains DotL, DotM and DotN and 5 additional proteins (Fig. 1a): IcmS, IcmW, LvgA, and two previously-uncharacterised proteins encoded by two annotated open reading frames, lpg0294 and lpg1549
Summary
Legionella pneumophila is a bacterial pathogen that utilises a Type IV secretion (T4S) system to inject effector proteins into human macrophages. In Legionella, DotL is part of a large complex that includes the proteins DotM and DotN (Supplementary Fig. 1a). Effector-bound IcmSW binds to T4CC through binding to the very C-terminal sequence of DotL (Supplementary Fig. 1a)[11,12,13].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
