Cryo-electron tomography of periplasmic flagella in Borrelia burgdorferi reveals a distinct cytoplasmic ATPase complex

• Published in: PLoS biology Vol. 16; no. 11; p. e3000050
• Main Authors: Qin, Zhuan, Tu, Jiagang, Lin, Tao, Norris, Steven J, Li, Chunhao, Motaleb, Md A, Liu, Jun
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 09.11.2018; Public Library of Science (PLoS)
• Subjects: Adenosine triphosphatase; Adenosine Triphosphatases - chemistry; Adenosine Triphosphatases - physiology; Adenosine Triphosphatases - ultrastructure; Assembly; Bacterial Proteins - chemistry; Bacteriology; Biology; Biology and Life Sciences; Borrelia burgdorferi; Borrelia burgdorferi - metabolism; Borrelia burgdorferi - physiology; Cytoplasm; E coli; Electron Microscope Tomography - methods; Flagella; Flagella - metabolism; Flagella - physiology; Flagella - ultrastructure; Laboratories; Lyme disease; Medical schools; Medicine; Medicine and Health Sciences; Morphology; Motility; Pathogenesis; Pathology; Periplasm - metabolism; Physical Sciences; Proteins; Rigidity; Salmonella; Secretion; Short Reports; Spirochetes; Spokes; Tomography; Type III Secretion Systems - metabolism; Type III Secretion Systems - ultrastructure; Vector-borne diseases; Visualization; United States > US; Virginia; Texas; Connecticut
• ISSN: 1545-7885; 1544-9173; 1545-7885
• DOI: 10.1371/journal.pbio.3000050

Periplasmic flagella are essential for the distinct morphology and motility of spirochetes. A flagella-specific type III secretion system (fT3SS) composed of a membrane-bound export apparatus and a cytosolic ATPase complex is responsible for the assembly of the periplasmic flagella. Here, we deployed cryo-electron tomography (cryo-ET) to visualize the fT3SS machine in the Lyme disease spirochete Borrelia burgdorferi. We show, for the first time, that the cytosolic ATPase complex is attached to the flagellar C-ring through multiple spokes to form the "spoke and hub" structure in B. burgdorferi. This structure not only strengthens structural rigidity of the round-shaped C-ring but also appears to rotate with the C-ring. Our studies provide structural insights into the unique mechanisms underlying assembly and rotation of the periplasmic flagella and may provide the basis for the development of novel therapeutic strategies against several pathogenic spirochetes.