Chapter 2 - Single Molecule Experiments and the Kinesin Motor Protein Superfamily: Walking Hand in Hand

Abstract

This chapter reviews the properties of kinesin, with special emphasis on how single molecule approaches have helped to reveal the motility mechanism of kinesin. It discusses a variety of experiments that have explored the behavior of individual kinesin motor proteins using single molecule techniques, such as optical tweezers and fluorescence microscopy. These experiments have helped to unravel the molecular mechanisms underlying the remarkable capabilities of these cellular motors. More and more single molecule studies currently explore nonconventional kinesins and report new features corresponding to additional binding modes and regulatory pathways. Additionally, the interaction between these motors and other proteins is increasingly becoming a subject of in vitro assays. To understand how kinesins convert the chemical energy obtained from the hydrolysis of ATP into the mechanical work of force generation and/or translocation, well-controlled in vitro motility assays, including the surface gliding assays and bead assays, have been used. Optical tweezers have been the method of choice to measure the forces of individual walking kinesin motors or apply controlled loads to them. Furthermore, experiments addressing the motility of individual motor proteins in living cells are now within reach. Since many members of the kinesin superfamily are still unexplored, new and exciting findings are likely to be revealed with the aid of these powerful techniques. The chapter also addresses diffusion along the microtubule lattice, a property of many kinesins, and the regulation of motor activity, an area of growing attention.