T4 RNA Ligase catalyzes the formation of phosphodiester bonds between single-stranded RNA or DNA containing 5'-phosphate and 3'-hydroxyl termini. The enzyme requires ATP for activity. The T4 RNA Ligase activity is highest for RNA-RNA ligation, lower for RNA-DNA ligation and lowest for DNA-DNA ligation. 3' end labeling is often completed using 5'-[32P]pCp.
The enzyme is supplied in a buffer of 20 mM Tris-HCl (pH 7.5), 50 mM NaCl, 1 mm DTT, 0.1 mM EDTA and 50% glycerol.