Intersubunit coordination and cooperativity in ring-shaped NTPases

Ring-shaped nucleoside triphosphatases (ring NTPases) are biological molecular machines powered by energy from NTP hydrolysis and are responsible for various cellular activities. These ring NTPases translocate their substrates or rotate their own subunits to/in the hole of the ring. Coordination and cooperativity among subunits in the oligomer ring is a topic of debate focused on understanding the operation mechanism of these protein machines. With the help of X-ray crystallographic structural analysis and optical microscopic single-molecules studies, distinct models, including stochastic, concerted, and rotary catalysis have been proposed. Here, we discuss these models and introduce high-speed atomic force microscopy as a new potent tool for verification of the model, with our recent example of the rotary catalysis of the stator ring of F1-adenosine triphosphatase.