Torque Spectroscopy for the Study of Rotary Motion in Biological Systems

Jan Lipfert, Maarten M. van Oene, Mina Lee, Francesco Pedaci, and Nynke H. Dekker

To understand the mechanistic basis of cellular function, immense efforts are undertaken to investigate the many different molecules that constitute a cell, aiming to probe both individual molecules as well as their interactions with others. Our understanding of the molecular basis of, for example, genome processing (including transcription, translation, and replication), the cytoskeleton and its dynamics, membrane assembly and composition, and cellular motion has grown tremendously in recent decades. Underlying the dynamics of many of these interactions are highly specialized enzymatic processes that facilitate specific chemical reactions. When these reactions are coupled to mechanical motion, the enzymes that perform the mechanochemical couplings are referred to as molecular machines, because they transduce chemical energy into mechanical work. DNA and RNA polymerases and helicases, protein translocases, kinesins and myosins, etc., are well-known examples of such molecular machines. Many such machines employ forces to execute linear motion, but it is also possible for a molecular machine to generate torques and to execute rotary motion. Indeed, in processes as distinct as bacterial swimming and the copying of DNA during replication, rotational motion and accompanying torques play key roles.

DOI