Transfer RNA. 3. Reconstitution of alanine acceptor activity from fragments produced by specific cleavage of tRNA Ala-II at its anticodon.

This report describes experiments showing that tRNA(Ala) (II) can be cleaved specifically at the G residue of its anticodon to give "half" molecules in high yield. Neither of these fragments has alanine-acceptor activity, but this activity can be reconstituted by mixing the fragments in the presence of Mg(+2). In dilute salt, on the other hand, the active complex dissociates spontaneously at 25 degrees into the two fragments. Thus, both "halves" of tRNA(Ala) (II) are necessary for acceptor activity and, in the presence of Mg(+2), combination of these fragments to give an active duplex is thermodynamically favorable.