Calorimetric characterization of the stable complex of myosin subfragment 1 with ADP and beryllium fluoride

Abstract
The thermal unfolding of the myosin subfragment 1 (S1) in its stable complex with ADP and beryllium fluoride (S1 · ADP · BeF3 ) was studied by differential scanning calorimetry. It has been shown that the structure of the S1 molecule in the S1 · ADP · BeF3 complex is similar to that of S1 in its complex with ADP and orthovanadate (S1 · ADP · Vi but differs radically from that of nucleotide‐free S1 and S1 in the S1 · ADP complex. It is concluded that the S1 · ADP · BeF3 complex can be considered, like the S1 · ADP · Vi complex, a stable structural analogue of the myosin head · ADP · Pi transition state of the myosin‐catalyzed ATP hydrolysis.