It has been discovered that this protein has a catalytic activity, in other words, it has the ability to increase the speed of chemical reactions which would not occur so fast. It is known to catalysis the following reaction (which requires the following cofactor: Mg(2+)):
                             ATP + RNA(n)  ⇄  diphosphate  +  RNA(n+1)
Depending on the surroundings the optimal pH varies from 8 in the cytoplasm to 8.3 in the nucleus.