Regulatory and catalytic domain dynamics of smooth muscle myosin filaments

Saturation-transfer electron paramagnetic resonance is used to determine the domain dynamics of the chicken gizzard smooth muscle myosin catalytic domain (heavy chain Cys-717) and regulatory domain (regulatory light chain Cys-108) in the absence of nucleotides. The results obtained are not consistent with a stable interaction between the two catalytic domains in unphosphorylated smooth muscle myosin filaments in the absence of nucleotides.