Bacterial Motility Machinery Laboratory
MINAMINO Group
Molecular mechanisms underlying bacterial flagellar assembly and function
Faculty
Research Summary
Many motile bacteria move through their environments using flagella. The bacterial flagellum is a large supramolecular complex that functions as a rotary molecular motor powered by the ion motive force across the cytoplasmic membrane. To construct this sophisticated nanomachine, flagellar building blocks are transported across the cytoplasmic membrane in a defined order by a specialized protein export apparatus located at the base of the flagellum, allowing the flagellum to be assembled efficiently.
Our laboratory aims to understand the fundamental principles governing how the bacterial flagellum is assembled and how it converts ion motive force into rotary motion. We combine genetic and biochemical analyses with biophysical approaches, including single-molecule measurements, and structural biology approaches, including X-ray crystallography and cryo-electron microscopy. Through these complementary approaches, we seek to elucidate the molecular and atomic mechanisms underlying flagellar assembly, protein export, and rotary motion.
Ultimately, our studies aim to uncover general design principles by which living organisms construct sophisticated molecular machines from nanoscale components and operate them with remarkable efficiency.
The bacterial flagellum is a large supramolecular complex consisting of a long helical filament extending from the cell surface, a flexible hook that functions as a universal joint, and a basal body that functions as an ion-driven rotary motor (A–C). Flagellar building blocks are transported across the cytoplasmic membrane by the flagellar-specific protein export apparatus located within the basal body and are sequentially assembled at the distal end of the growing flagellum. By integrating genetics, biochemistry, biophysics, and structural biology, we investigate the molecular mechanisms underlying flagellar assembly, protein export, and rotary motion. D shows the atomic structure of the FliPQR protein-export channel determined by cryo-electron microscopy.
Selected Publications
- Kinoshita M, Miyata T, Makino F, Imada K, Namba K, Minamino T. A β-cap on the FliPQR protein-export channel acts as the cap for initial flagellar rod assembly. Proc. Natl. Acad. Sci. USA 122, e2507221122 (2025) https://doi.org/10.1073/pnas.2507221122
- Kinoshita M, Makino F, Miyata T, Imada K, Namba K, Minamino T. Structural basis for assembly and function of the Salmonella flagellar MS-ring with three different symmetries. Commun. Biol.8, 61 (2025). https://doi.org/10.1038/s42003-025-07485-2
- Minamino T, Morimoto YV, Kinoshita M, Namba K. Membrane voltage-dependent activation mechanism of the bacterial flagellar protein export apparatus. Proc. Natl. Acad. Sci. USA 118, e2026587118 (2021). https://doi.org/10.1073/pnas.2026587118
- Nakamura S, Hanaizumi Y, Morimoto YV, Inoue Y, Erhardt M, Minamino T, Namba K. Direct observation of speed fluctuations of flagellar motor rotation at extremely low load close to zero. Mol. Microbiol. 113, 755–765 (2020). https://doi.org/10.1111/mmi.14440