Experiments were carried out to explore the location of thiol groups which became less reactive when S2 became more reactive in the presence of ADP. Myosin was first treated with N-ethylmaleimide to block S1 and then treated with a fluorogenic thiol reagent, N-(7-dimethyl-amino-4-methylcoumarinyl) maleimide (DACM), in the presence or absence of ADP. From the distribution of DACM in the two kinds of DACM-treated myosin, it was found that thiol groups of all the light chains and of the 50 K fragment of subfragment-1 heavy chain became less reactive to DACM in the presence of ADP. Since it is known that the ADP binding site and S2 are located in the 26 K and 21 K fragments of subfragment-1 heavy chain, respectively, our results suggest that the 50 K, 26 K, and 21 K fragments of subfragment-1 heavy chain and light chains are closely connected with each other in the subfragment-1.
Thiols of myosin. VI. Effect of ADP on the reactivity of thiol groups other than S2. Publishing Authors By Initials
