CALORIMETRIC STUDIES ON THE STABLE COMPLE XES OF MYOSIN SUBFRAGMENT-1WITH ADP AND PHOSPHATE ANALOGS

This short review is concerned with the application of the method of d ifferential scanning calorimetry to study the conformational changes o f isolated myosin head (myosin subfragment 1, S1) caused by the format ion of the S1 complexes with Mg2+-ADP and P-i analogues such as orthov anadate (V), aluminum fluoride (AIF(4)(-)) or beryllium fluoride (BeFx ). These changes of the whole S1 molecule are reflected in a significa nt increase of S1 thermal stability and in a pronounced increase of th e cooperativity of the thermal denaturation. Since the complexes S1-AD P-V, S1-ADP-AlF4- and S1-ADP-BeFx are stable analogues of the S1*-ADP -P-i transition state of the S1-catalyzed ATP hydrolysis, it is conclu ded that DSC studies with these complexes offer a new and promising ap proach to investigate the structural changes which occur in the myosin head during Mg2+-ATPase reaction.