Cytoskeletal motors perform critical force generation and transport functions in eukaryotic cells. Engineering molecular motors can provide direct tests of structure-function relationships and potential tools for controlling cellular processes or for harnessing molecular transport in artificial systems. I will discuss the recent design and characterization of a panel of cytoskeletal motors that reversibly change gears — speed up, slow down, or switch directions — when exposed to blue light. Genetically encoded light-responsive motors will expand the optogenetics toolkit, complementing precise perturbations of ion channels and intracellular signaling with spatiotemporal control of cytoskeletal transport and contractility.
Simultaneous measurements of DNA twist and extension have been used to measure physical properties of the double helix and to characterize structural dynamics and mechanochemistry in nucleoprotein complexes. I will discuss the development of gold rotor bead tracking (AuRBT), which enables a >100X improvement in time resolution over previous twist measurement techniques. In an initial application to molecular motor mechanism, we have examined the structural dynamics of DNA gyrase at previously inaccessible timescales, revealing an unanticipated transient state visited during active supercoiling.