RNA POLYMERASE - Types EASY NOTES

• The information present on the template strand of DNA is transcribed for the formation of single-stranded RNA with the help of the enzyme DNA dependent RNA polymerase.

RNA polymerase in mammals :

there are three types:

1. RNA P-type I/A -

-involved in the synthesis of ribosomal RNA (r-RNA)

-it is not inhibited by amanitin. 

(amanitin is a toxin from the mushroom Amanitin phalloides).

2.RNA P-type II/B

-involved in the synthesis of messenger RNA (m-RNA), Small nuclear RNA(snRNA).

-it is inhibited by amanitin.

-it is made up of 2 large and 12 small subunits.

-it is activated by phosphorylation

3.RNA P-type III/C

-involved in synthesis of transfer RNA(t - RNA)

-it is moderately inhibited by amanitin. (amanitin is a toxin from the mushroom Amanitin phalloides).

RNA polymerase in Bacteria :

-it is made up of 2 alpha, 2 beta,1 omega, 1 sigma, and 2 zinc molecules.

-the promoter sit is recognized by the sigma factor.

-sigma factor also increases the affinity of the enzyme towards the promoter site.

-fixation to initiation site is with the help of beta unit