[Substrate specificity of T4 RNA-ligase. The effect of the nucleotide composition of substrates and the size of phosphate donor on the effectiveness of intermolecular ligation].

Nucleoside 2' (3'),5'-diphosphates, dinucleotides pApA, pApC, pApU, pGpC, pCpC, pUpU (phosphate donors), and trinucleoside diphosphates, such as NpCpC, NpCpU, NpUpC, NpUpU and GpApN (N = U, C, A or G; phosphate acceptors) were used to study the substrate specificity of T4 RNA ligase. Relative efficiency of the mono- and dinucleotide donors depends on the 5'-terminal nucleoside moiety of the dinucleotide: upon ligation with the minimal phosphate acceptor GpUpC, dinucleotides pApA, pApC, and pApU are more effective than nucleotide diphosphate pAp; pGpC is more effective than pGp; efficiencies of pCpC and pCp are almost identical, and efficiency of pUpU is slightly lower than that of pUp. In relative efficiency, dinucleotide donors, varying only in 5'-terminal unit, do not correspond to mononucleotides: pApC greater than pCpC greater than pGpC and pCp greater than pUp approximately pAp much greater than pGp. The effects observed for homooligomeric substrates cannot be extra-polated on heterooligomers.