[Substrate specificity of T4 RNA-ligase. The effect of the nucleotide sequence of the minimum phosphate acceptor on the efficacy of intermolecular ligation].

The 2' (3'),5'-diphosphates of cytidine, uridine, adenosine and the trinucleoside diphosphates, such as NpCpC, NpCpU, NpUpC, NpUpU and ApNpC (where N = U, C, A, G), were used to study the substrate specificity of the T4 RNA ligase. The outcome of ligating various phosphate acceptors to a common phosphate donor was governed not only by nucleotide composition but also the nucleotide sequence of a phosphate acceptor. The effect of the changes in a single position of the phosphate acceptor on the efficiency of the intermolecular ligation cannot be defined independently of the other nucleotide residues. For four examined groups of phosphate acceptors and pCp as a donor, four different ranks were obtained (in order of decreasing reactivity): C greater than A greater than greater than U greater than G (for NpCpC); G greater than U approximately equal to A greater than C (NpCpU); A greater than U greater than C greater than G (NpUpC) and A greater than G greater than C greater than U (NpUpU). The yield of ligation products with various phosphate donors and a common phosphate acceptor significantly depends on the donor structure: pyrimidine phosphate donors are more effective than pAp, while pCp is more effective than pUp.