DESCRIPTION. The long range goal of this research is to provide a better understanding of the mechanism of movement of intracellular organelles along microtubules, Such movement plays a special role in the process of fast axonal transport in nerve cells. This process provides one means for the movement of newly synthesized material from their site of synthesis in the body of a nerve cell to the synapse at the end of the axon. Kinesin has been found in a wide range of higher eukaryotes and are present in most cell types, not just neurons. In these other cell types, kinesin is likely responsible for the related transport of some classes of membrane vesicle towards the periphery of the cell. Other proteins that are related to kinesin are responsible for part of the movement along spindle microtubules during cell division. Information developed in the proposed study will also be applicable to these other important motor proteins. The energy that drives the movement of kinesin is provided by the hydrolysis of adenosine triphosphate (ATP). A principal aim of the proposed work is to determine the detailed enzymatic mechanism of ATP hydrolysis with emphasis on how the chemical energy change of hydrolysis is coupled to the physical generation of movement along a microtubule. Because the movement results from changes in the conformation of the enzyme, it is also important to understand the structure of the enzyme and how it changes during catalysis. One ongoing approach is characterization of the individual domain of kinesin. Recent progress indicates that kinesin is folded in vivo into an inhibited form that needs to unfold before it can be an active motor. The folding is produced by the interaction of regions in the two ends of the protein and the study of the regulation of the folding process and factors influencing it will be performed. Extensive use will be made of steady and single turnover kinetics in the investigation of the mechanism. These enzymatic studies will be coupled with study of the motility that kinesin is able to produce. A long range goal is to be able to model the physical properties of kinesin based on its solution biochemical mechanism,