[Calorimetric study of stable complexes of myosin subfragment I with adenosine diphosphate and phosphate analogs]

This short review is concerned with the application of the method of differential scanning calorimetry to study the conformational changes of isolated myosin head (myosin subfragment 1, S1) caused by the formation of the S1 complexes with Mg(2+)-ADP and P(i) analogues such as orthovanadate (V), aluminium fluoride (AIF4-) or beryllium fluoride (BeFx). These changes of the whole S1 molecule are reflected in a significant increase of S1 thermal stability and in a pronounced increase of the cooperativity of the thermal denaturation. Since the complexes S1-ADP-V, S1-ADP-AIF4- and S1-ADP-BeFx are stable analogues of the S1**-ADP-P(i) transition state of the S1-catalyzed ATP hydrolysis, it is concluded that DSC studies with these complexes offer a new and promising approach to investigate the structural changes which occur in the myosin head during Mg(2+)-ATPase reaction.