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.