Purification of Na⁺-Driven MotPS Stator Complexes and Single-Molecule Imaging by High-Speed Atomic Force Microscopy

The stator unit of the bacterial flagellar motor coordinates the number of active stators in the motor by sensing changes in external load and ion motive force across the cytoplasmic membrane. The structural dynamics of the stator unit at the single-molecule level is key to understanding the sensing mechanism and motor assembly. High-speed atomic force microscopy (HS-AFM) is a powerful tool for directly observing dynamically acting biological molecules with high spatiotemporal resolution without interfering with their function. Here, we describe protocols for single-molecule imaging of the Na⁺-driven MotPS stator complex by HS-AFM.