Multi-subunits RNA polymerase:

Multi-subunit RNA polymerase structure (using RNA polymerase II as an example), different colored rectangles indicate different subunits.Table of subunits corresponding to each domain of multi-subunit RNA polymerase, and their functions is shown.

Single-subunits RNA polymerase:

The single-subunit RNA polymerase structure is shown, which contains three domains: fingers domain (yellow), Thumb domain (green), and Palm domain (red). Almost all single-subunit RNA polymerases have these three domains.