Regulation of contraction by calcium binding myosins.

Contraction of molluscan muscles is triggered by binding of Ca2+ to myosin. Molluscan myosins are regulated molecules, their light chains serve as regulatory subunits. They differ from myosins of skeletal muscles in requiring Ca2+ for activity and having a specific high-affinity Ca2+ binding site. As all conventional myosins molluscan myosins also consist of two heavy chains, two regulatory and two essential light chains. Scallop myosin is particularly suitable for studying light chain function since its regulatory light chains readily dissociate in the absence of divalent cations and its essential light chains can be exchanged with foreign light chains. The structural, mutational and biochemical studies presented here are aimed to elucidate the role of the light chains in regulation, to describe the interactions between the myosin subunits and to locate the regions and the amino acids responsible for the differences between functional and non-functional light chains.