Structure-activity Relationships In Synthetic Systems Of Coupled Motor Proteins

Abstract

Motor proteins play an essential role in regulating the internal organization of the cytoplasm by maneuvering a wide variety of vesicles and organelles. Many of these transport processes depend on the ability of motors to function collectively, in groups that contain more than one motor molecule. Utilizing protein engineering and DNA-self-assembly techniques, we have created experimental models of these multi-motor systems. Our synthetic assemblies afford precise control over the number of coupled motors in a construct, as well as their relative positions and the mechanical compliance of the linkage between each motor and the solid support to which it is anchored. Furthermore, the molecular architecture of these assemblies has been characterized using both bulk methods and single-molecule microscopy techniques. Our initial optical trapping experiments revealed rich behavior in a system of two coupled kinesin motors; the force-velocity relationship for individual constructs reveals that coupled kinesin motors can move at higher-than-predicted velocities when under high loads. Additionally, the system's stepping dynamics appears to vary significantly with applied load. Here, we discuss our efforts to characterize the effect of mechanical compliance and inter-motor separation upon these behaviors. Understanding these structure-activity relationships is critical to our broader goal of a comprehensive, mechanistic model of collective motor protein transport. Such a model would provide important insight into the process by which a cell controls its internal order.