Architecture of the type IVa pilus machine

• Published in: Science (American Association for the Advancement of Science) Vol. 351; no. 6278; p. 1165
• Main Authors: Chang, Yi-Wei, Rettberg, Lee A., Treuner-Lange, Anke, Iwasa, Janet, Søgaard-Andersen, Lotte, Jensen, Grant J.
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 11.03.2016; The American Association for the Advancement of Science
• Subjects: Architecture; Bacterial Adhesion; Bacterial proteins; Bacteriology; Cellular biology; Cryoelectron Microscopy; Fimbriae, Bacterial - genetics; Fimbriae, Bacterial - ultrastructure; Membranes; Microscopy, Electron, Transmission; Models, Molecular; Mutation; Myxococcus xanthus - genetics; Myxococcus xanthus - physiology; Myxococcus xanthus - ultrastructure; RESEARCH ARTICLE SUMMARY; Scientific imaging
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.aad2001

Type IVa pili are filamentous cell surface structures observed in many bacteria. They pull cells forward by extending, adhering to surfaces, and then retracting. We used cryo-electron tomography of intact Myxococcus xanthus cells to visualize type IVa pili and the protein machine that assembles and retracts them (the type IVa pilus machine, or T4PM) in situ, in both the piliated and nonpiliated states, at a resolution of 3 to 4 nanometers. We found that T4PM comprises an outer membrane pore, four interconnected ring structures in the periplasm and cytoplasm, a cytoplasmic disc and dome, and a periplasmic stem. By systematically imaging mutants lacking defined T4PM proteins or with individual proteins fused to tags, we mapped the locations of all 10 T4PM core components and the minor pilins, thereby providing insights into pilus assembly, structure, and function.