Abstract
A motor protein moves on a large scale at molecular level. We have used site-directed spin-labeling electron spin resonance (ESR) to detect molecular orientation, residual side-chain mobility and inter-residual distances. Especially, the distances of 8-80 Å can be measured by continuous-wave and recently developed pulse ESR. We applied these techniques to the studies on conformational dynamics of motor proteins, myosin and kinesin, and muscular switch proteins troponin-tropomyosin. In these systems, the flexible elements undergo thermal motion and fluctuate on large scale between distinct structural states during activity.
