Kinetic and equilibrium analysis of the interactions of actomyosin subfragment-1.ADP with beryllium fluoride.

The hypothesis that the stable ternary complex formed between myosin subfragment-1, MgADP and beryllium fluoride (BeF 3 - ), denoted S-1¬=;.ADP.BeF 3 - , is an analog of the intermediate state S-1 ** .ADP.P i has been tested in this work by examining the interactions of S-1¬=;.ADP.BeF 3 - complex (K a =10 4 M -1 ) in the presence of 40 mM KCl. The stability of this complex was strongly salt-dependent. The association constant of BeF 3 - to the acto-S-1.ADP complex (K Be ∼10 3 M -1 ) was 100-fold weaker than its binding to the S-1.ADP complex