REACTIVITIES OF CYS(707) (SH1) IN INTERMEDIATE STATES OF MYOSIN SUBFRAGMENT-1 ATPASE

To detect structural changes around the reactive Cys(707) (SH1) in the myosin heavy chain during the ATPase reaction, the reactivity of SH1 in rabbit skeletal myosin subfragment-1 (S-1) was measured using a flu orescent reagent, 5-(iodoacetamidoethyl)aminonaphthalene-1-sulfonic ac id, in the presence of various ATP analogs: adenosine 5'-(3-thiotripho sphate) (ATP gamma S), ADP-vanadate (ADP-V-i), ADP-BeFx, and ADP-AlF4. The SH1 reactivities in the S-1 complexes with ATP gamma S and ADP-Be Fx, analogs of the E-ATP state, were very high, as well as that in the E-ADP state. In contrast, the SH1 reactivities in the S-1 complexes w ith ADP-V-i and ADP-AlF4, analogs of the E-ADP-P state, were extremely low. The structural changes around SH1 can be correlated to changes i n the structure of the gamma-phosphate of ATP during the ATPase reacti on or to the structure of the corresponding part of ATP analogs at the active site of ATPase, This is consistent with the crystal structure of S-1 in which the heavy chain structure around SH1 of S-1-ADP-BeFx i s significantly different from those of S-1-ADP-V-i and S-1-ADP-AlF4 [ Fisher et al, (1995) Biochemistry 34, 8960-8972; Smith and Rayment (19 96) Biochemistry 35, 5404-5417].