The molecular mechanisms by which troponin and tropomyosin regulate the interaction of actin and myosin in skeletal muscle will be investigated, involving a detailed study of the changes in structure and interactions among the troponin subunits and the other thin filament proteins, actin and tropomyosin. This will be approached by studying a) details of the strength and sites of intersubunit binding between TnC, TnI and TnT; b) the transfer of metal-induced structural information to proteins forming complexes with TnC; c) the effects of actin-myosin interactions on the cooperativity of Ca2+ binding to troponin. The major experimental tools for these studies will be optical and magnetic spectroscopy and hydrogen/tritium exchange studies. It is expected that the study presented in this proposal may contribute to an understanding of the regulatory processes in muscles. New knowledge developed here on metal-protein and protein-protein interactions should be of significance in the general fied of protein chemistry since similar processes are widely distributed among biological systems in a variety of physiological processes. Finally, knowledge about normal muscle function is essential for the eventual understanding of the molecular mechanisms underlying disease processes in muscle.