Motor proteins of the kinesin superfamily move a diverse set of cargo molecules along the microtubules that are a critical part of the cytoskeletal framework of cells. Movement is coupled to ATP hydrolysis and, although the mechanism for generating movement is becoming well understood, comparatively little is known about how the process is regulated. This proposal will address the role of autoinhibition of soluble kinesin-1, the founding member of the superfamily and the motor responsible for driving the process of fast axonal transport in axons and related movements in all cells. Experiments are proposed to determine the importance of the different factors that contribute to autoinhibition and how they can be reversed by regulatory signals. An important aspect is how cargo molecules are selected for attachment to kinesin-1 so that they can be transported. Post-translational modification of the motor or cargo will be investigated as one mechanism by which the process can be controlled. An additional component is an investigation of how auxiliary microtubule binding sites can modulate and regulate the motile properties of the motors. All kinesin motors use their 'motor domains'to interact with the microtubule track along which they move. It is the series of conformational changes coupled to the hydrolysis of ATP that drives the movement of the motor along the track. Many kinesin superfamily members, as well as many cargo molecules, contain additional regions outside of the motor domains that bind to microtubules in a manner that is independent of ATP and not energy-linked or directly involved in generation of movement. Simultaneous binding of both the motor domains and the additional site to the microtubule has the potential to greatly increase the net affinity for the microtubule and allow the motor to make longer runs along a microtubule before falling off. Kinesins play a central role in moving specific cellular components to their proper intracellular position. Disruptions of the genes for several kinesins have severe consequences for the cell and understanding how these motors are controlled will help provide insight into possible therapies. PUBLIC HEALTH RELEVANCE: Kinesin is a motor protein that will be studied. It moves cargoes inside the cell to their proper location. This is especially critical in nerve cells because of the long length of their axons. One of the critical cargoes moved by kinesin is amyloid precursor protein (APP) and inhibition of its proper transport in the cell may be a factor in Alzheimer's disease.