Complexes of myosin subfragment 1 with pyrophosphate and with adenosine diphosphate as studied by phosphorus-31 nuclear magnetic resonance.

Myosin subfragment-1.pyrophosphate (S1.PPi) complex and S1.ADP complex were observed with 31P NMR at various temperatures between 0 and 25 degrees C. The signal of S1.PPi complex showed a small temperature dependence, indicating that a single conformation exists for the complex. It also showed that the electron density around phosphorus nuclei was increased upon the formation of complex. On the other hand, the signal of S1.ADP complex was clearly dependent on temperature and indicated the presence of two forms, i.e., high-temperature and low-temperature forms. In the high-temperature form, the electron density around beta-phosphate was decreased upon the formation of complex with S1. In the low-temperature form, the distribution of electrons around phosphorus nuclei is extremely anisotropic due to the tight interaction of S1 and the phosphate moieties of ADP.