THE DIFFERENCE BETWEEN ADP-BERYLLIUM FLUORIDE AND ADP-ALUMINUM 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 (AIF(4)), 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-AIF(4) 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-AIF(4) and S1-ADP-BeFx complexes represent structural analogues of different transition states of the ATPase cycle, namely the intermediate states S1**-ADP-P-1 and S1*-ATP, respectively.