RNA Polymerase

I.U.B.: 2.7.7.6

Enzymatic Reaction (image will open in a new window) 

Nucleoside-triphosphate:RNA nucleotidyltransferase (DNA-directed)

E.coli DNA-dependent RNA polymerase catalyzes the initiation (site selection), elongation and termination of polyribonucleotide chains, using ribonucleoside triphosphates as substrates and DNA as template.

Characteristics of RNA Polymerase from E. coli:

Molecular weight:

The enzyme consists of four major subunits designated β',β, α, and σ with molecular weights in that order: 160, 150, 86, 40 Kda.

Composition:

The enzyme has a complex subunit structure with two configurations designated RNA polymerase holoenzyme and core RNA polymerase exhibiting enzymatic activity. The holoenzyme has the subunit composition σ₂'ββα,and can be resolved into two components: the core enzyme σ₂'ββ and the sigma factor. The holoenzyme appears to be involved in the synthesis of most cellular RNA.

Activators and inhibitors: E. coli RNA polymerase has absolute requirements for divalent metal ions such as Mg⁺⁺, Mn⁺⁺, or Co⁺⁺. Rifampicin, streptovaricins, streptolydigin, and sulfydryl reagents are among the inhibitors of E.coli RNA polymerase.