RNA Ligase

A short video describing the basics of how RNA ligase enzymes tend to work.

Video Transcript: RNA ligase has a very important job. It ligates, or joins together, two strands of mRNA. The interesting question is, how does it work? To answer this, we need to look at the structure of RNA ligase. If you zoom in on the protein surface, you will find a lysine residue. The nitrogen, shown in blue, starts the whole process off. The lysine attaches to a molecule of adenosine triphosphate (ATP) causing two phosphate groups to leave. This forms adenosine monophosphate (AMP). The lysine residue then hands off the AMP to the 5’ phosphate group located on one of the mRNA strands. After the AMP is in place, the hydroxyl group on the other strand can attack, kicking off the AMP and forming a new phosphodiester bond. That is the basics of how RNA strands are ligated together. RNA ligase does more than just handle the ATP though. The whole ligation reaction proceeds only when the enzyme has everything bound to it, and at least for some RNA ligases, like T4 RNA ligase, the ligase does not act alone. T4 RNA ligase needs another enzyme, T4 PNK, to come and change the 3’ and 5’ ends to allow T4 RNA ligase to work.