Spectroscopic probes of muscle proteins

The use of site-directed spectroscopic probes in elucidating the molecular mechanism of force generation in muscle is reviewed, focusing on recent technical and conceptual advances. High-resolution crystal structures of actin and myosin suggest mechanistic models for force generation, but spectroscopic probe experiments under functional conditions are required to test and refine these models. An array of complementary spectroscopic techniques has been developed that can detect disorder and dynamics directly, resolve multiple conformational states, and can be applied to complex protein assemblies, taking advantage of the beautiful symmetry of the myofibrillar lattice. Recently developed instrumentation has the capacity to resolve simultaneously both biochemical and structural kinetics of myosin and/or actin. These new insights support a model in which structural and biochemical transitions are not tightly coupled, and disorder-to-order transitions play central roles in both force generation and its regulation.