The role of myosin heads in the process of myosin and sarcomere assembly will be investigated. Work in progress indicates that expression of myosin heads lacking rod sequence disrupts sarcomere organization in the nematode, Caenorhabditis elegans. Experiments are proposed to define regions of the myosin head responsible for the muscle-disruptive effect and to determine the gate of truncated myosin molecules. Transgenic nematodes expressing full-length myosin or myosin head fragments will be produced. The motility and muscle ultrastructural defects of control and experimental transgenic worms will be compared. The smallest myosin fragment which disrupts muscle organization will be characterized. %%% The contractile mechanism of muscle tissue consists of two major proteins, myosin and actin, which are arranged (along with other auxiliary proteins) in densely packed, highly ordered arrays termed sarcomeres, such that linear arrays of myosin molecules (the "motor" for contractile movement, which transduces chemical energy into mechanical energy) move along actin filaments (which serve as the "track"), resulting in shortening of the sarcomere (and hence of the muscle itself). This project is concerned with the role of the myosin molecules in the assembly of the contractile apparatus. The power of genetic manipulations will be employed to engineer nematodes with myosin molecules bearing mutations at specific sites, to determine the functional consequence of these specific mutations. An understanding of the structural requirements for contractile machinery assembly is a necessary prerequisite to biotechnological applications of biomolecular motors. Given the high degree of conservation among myosins throughout the animal kingdom, it is expected that the results obtained with the nematode model system will be generally applicable to other animals.
