Role of the unique loops located in the dotor domain of myosin and kinesin

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The structure of the motor domains of myosin and kinesin are highly conserved. Thus, these motor proteins may share a common mechanism for generating energy for from ATP hydrolysis. Nevertheless, myosin and kinesin have several unique loops in each motor domain. The precise function of the loops is as yet known, but they may have roles in determining the characteristic properties of each motor protein. In the present study, the conformational changes of the loops in ATPase were studied using several biochemical and molecular biological techniques and the experimental results suggested that the loops might act as a signal transducer mediation communication between ATP binding site and action or microtubules binding site.For unique loops of myosin, using fluorescent reasonance energy transfer technique, It has been demonstrated that the conformation of the loop M changes during the ATPase cycle, suggesting th that loop M acts as a signal transducer mediating communication between the ATPbinding -and action-binding site.For unique loops of kinesin, the results of molecular biological experiments indicated that the loop L5 in kinesin motor domain determins the gliding velocity of microtubules.