The difference between ADP-beryllium fluoride and ADP-aluminium fluoride complexes of the spin-labeled myosin subfragment 1.

Electron paramagnetic resonance (EPR) spectroscopy was used for investigation of the structure of spin-labeled myosin subfragment 1 (S1) containing ADP and phosphate analogues, such as orthovanadate, aluminium fluoride (AlF4), and beryllium fluoride (BeFx). It has been shown that the local conformational changes in the region of Cys-707, induced by formation of the S1-ADP-BeFx complex, differ from those of S1 containing ADP-AlF4 or other phosphate analogues but are similar to the changes which occur in the presence of ADP or ATP gamma S. It is suggested that S1-ADP-AlF4 and S1-ADP-BeFx complexes represent structural analogues of different transition states of the ATPase cycle, namely the intermediate states S1**-ADP-P(i) and S1*-ATP, respectively.