The effect of the replacement of ADP with a photoaffinity ATP analogue, 2‐azido‐ADP, in F‐actin on its function

Abstract
2‐Azido‐ATP, a photoaffinity ATP analogue, was incorporated into actin and the influence of the incorporation on the actin function was studied. The replacement of ADP with 2‐azido‐ADP in F‐actin both before and after photocross‐linking decreased appreciably the actin‐activated S1‐ATPase activity. Photocross‐linked 2‐azido‐ADP‐F‐actin could be depolymerized by dialysis against a solution containing 0.1 mM CaCl2, 0.1 mM ATP and 1 mM Tris‐HCl (pH 8.0). However, once it depolymerized, it lost very quickly the ability to polymerize even in the presence of a sufficient amount of ATP and Ca2+.