Controllable Molecular Motors Engineered from Myosin and RNA

Abstract

Engineering biomolecular motors can provide direct tests of structure-function relationships and customized components for controlling molecular transport in artificial systems or in living cells. In previous work, synthetic nucleic acid motors have been designed from first principles and engineered for versatile programmable control; in a complementary approach, natural protein motors have been modified to combine some control and tunability with favorable evolved properties such as speed, processivity, and biological compatibility. Nucleoprotein motors such as the ribosome illustrate the potential for tightly integrating protein and nucleic acid components to enable sophisticated functionality. However, this potential has only begun to be explored in pioneering work harnessing DNA scaffolds to dictate the spacing, number, and composition of tethered protein motors. Here, we describe myosin motors that incorporate RNA lever arms, forming hybrid assemblies in which conformational changes in the protein motor domain are amplified and redirected by nucleic acid structures. The RNA lever arm geometry determines the speed and direction of motor transport, and can be dynamically controlled using programmed transitions in lever arm structure. We have characterized the hybrid motors using in vitro assays of propelled actin filaments, single-molecule tracking of tetrameric processive walkers, cryoelectron microscopy, and MOHCA-seq structural probing. Our results confirm the operation of motors designed to reversibly change direction in response to oligonucleotide signals that drive strand-displacement reactions. This work enables future applications in which complex transport systems are programmed using sequence-addressable control of speed and direction in heterogeneous motor collections; in principle, the signaling inputs can originate from transcriptional circuits or DNA computations. Similar combinations of nucleic acid structures and diverse protein motors may provide a general strategy for controlling dynamic behavior, with collective motor properties further determined by precise arrangement and orientation on larger nucleic acid scaffolds.