1. Molecular architecture, polar targeting and biogenesis of the Legionella Dot/Icm T4SS
- Author
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Grant J. Jensen, Jacob Gyore, KwangCheol Casey Jeong, Adam Gardner, Joseph P. Vogel, Lin Teng, Debnath Ghosal, and Yi-Wei Chang
- Subjects
Microbiology (medical) ,Electron Microscope Tomography ,Immunology ,Applied Microbiology and Biotechnology ,Microbiology ,Legionella pneumophila ,Article ,Cell membrane ,Type IV Secretion Systems ,03 medical and health sciences ,Bacterial Proteins ,Organelle ,Cell polarity ,Genetics ,medicine ,Secretion ,030304 developmental biology ,0303 health sciences ,biology ,030306 microbiology ,Chemistry ,Cell Membrane ,Cell Polarity ,Cell Biology ,Periplasmic space ,biology.organism_classification ,Transmembrane protein ,Cell biology ,medicine.anatomical_structure ,Microscopy, Fluorescence ,embryonic structures ,Mutation ,Periplasm ,Protein Multimerization ,Biogenesis - Abstract
Legionella pneumophila survives and replicates inside host cells by secreting ~300 effectors through the defective in organelle trafficking (Dot)/intracellular multiplication (Icm) type IVB secretion system (T4BSS). Here, we used complementary electron cryotomography and immunofluorescence microscopy to investigate the molecular architecture and biogenesis of the Dot/Icm secretion apparatus. Electron cryotomography mapped the location of the core and accessory components of the Legionella core transmembrane subcomplex, revealing a well-ordered central channel that opens into a large, windowed secretion chamber with an unusual 13-fold symmetry. Immunofluorescence microscopy deciphered an early-stage assembly process that begins with the targeting of Dot/Icm components to the bacterial poles. Polar targeting of this T4BSS is mediated by two Dot/Icm proteins, DotU and IcmF, that, interestingly, are homologues of the T6SS membrane complex components TssL and TssM, suggesting that the Dot/Icm T4BSS is a hybrid system. Together, these results revealed that the Dot/Icm complex assembles in an ‘axial-to-peripheral’ pattern.
- Published
- 2019