RtcB Ligase from E. coli joins single stranded RNA with a 3' -phosphate or 2' ,3' -cyclic phosphate to another RNA with a 5' -hydroxyl. Ligation requires both GTP and MnCl2 and proceeds through a 3' -guanylate intermediate . For substrates with a 2' ,3' -cyclic phosphate end, hydrolysis to a 3' -phosphate precedes 3' end activation with GMP and ligation.
