This research program is focused on three inter-related questions concerning regulation of muscle contraction: the molecular basis for calcium-dependent control by myosin, the role of protein phosphorylation and filament architecture in regulating long-lasting contractions, and the structure and dynamics of the calcium-pumping protein assembly in the sarcoplasmic reticulum membrane. In each case, the goal is to relate the detailed structure and properties of individual protein molecules to the architecture and dynamics of the native protein assemblies in muscle. Drs. Vibert and Cohen have established that certain invertebrate muscles are especially suitable for these investigations, and that their structural and regulatory properties are of general significance for contraction in many muscle types, including those of vertebrates. In the next phase of this program, application of advanced methods of electron microscopy - especially cryo-electron microscopy of vitrified samples - should provide images of higher resolution and fidelity than have been produced in the past. Coupled with the use of proteins altered by site-directed mutagenesis, and of specific antibodies, these structural approaches should allow them to integrate findings at the molecular level into a picture of regulation in whole muscle. Knowledge of the structure and switching of the protein assemblies that regulate muscle contraction involves understanding inter-related control systems at a higher level of organization than any yet achieved.
