Biological Nanomotors with Linear, Rotation, or Revolution Motion Mechanism

The ubiquitous biological nanomotors were once classified into two categories: linear and rotation motors. In 2013, a third type of biomotor—revolution without rotation (see animations: https://nanobio.uky.edu/movie.html" xmlns:xlink="https://www.w3.org/1999/xlink">https://nanobio.uky.edu/movie.html)—was discovered and found to be widespread among bacteria, eukaryotic viruses, and dsDNA bacteriophages. This review focuses on recent findings of various aspects of motors, including chirality, stoichiometry, channel size, entropy, conformational change, and energy usage rate in a variety of well-studied motors, including FOF1 ATPase, helicases, viral dsDNA-packaging motors, bacterial chromosome translocases, myosin, kinesin, and dynein. In particular, dsDNA translocases are used to illustrate how these features relate to the motion mechanism, and how nature elegantly evolved a revolution mechanism to avoid coiling and tangling during lengthy dsDNA genome transportation in cell division. Motor chirality and channel size are the two factors to distinguish rotation motors from revolution motors. Rotation motors use the right-handed channels to drive the right-handed dsDNA, similar to the way a nut drives the bolt with threads in the same orientation; revolution motors use the left-handed motor channels to revolve the right-handed dsDNA. Rotation motors use small channels (< 2 nm in diameter) for the close contact of the channel wall with the 2-nm dsDNA bolt; revolution motors use larger channels (> 3 nm in diameter) with room for the bolt to revolve. Binding and hydrolysis of ATP are linked to different conformational entropy changes in the motor that lead to altered affinity for the substrate and allow work to be done, for example, unwind DNA in a helicase, or move DNA directionally for a translocase.