The main goal of our research is to understand how muscle functions at the molecular level. The system that we study is the indirect muscle of the fruit fly Drosophila melanogaster. AMong the many advantages that this system offers for molecular studies is the fact that these muscles are expendable for viability and therefore amenable for genetic and molecular-genetic analyses. During the course of our investigation, we identified a novel muscle protein that does not resemble any known protein. We hypothesize that this protein is involved in regulation of muscle contraction. Our goal for this proposal is to identify and characterize mutations that affect the gene encoding this protein. We will then analyze the effect of the mutant protein on the ultrastructural, biochemical and mechanical properties of the muscle. These studies will provide valuable information on the biological function of this protein and on the mechanisms regulating force generation during muscle contraction.