RNA-Polymerase

RNA polymerases, more DNA -dependent RNA polymerases are enzymes ( polymerases) that catalyze the synthesis of ribonucleic acids (RNA) in the transcription of the DNA.

In bacteria, there is only one form of RNA polymerase, primase.

In eukaryotes, there are three forms of RNA polymerase:

These RNA polymerases are DNA - dependent.

The RNA polymerase II and III are inhibited by α - amanitin.

The RNA polymerases are composed very complex. In the yeast ten different polypeptide chains whose molecular mass are 7700-140000 Dalton, magnesium, zinc, and two DNA chains are involved. Overall, these RNA polymerase consists of over 28,000 atoms.

RNA polymerases have a simple mechanism for error detection: If attaches an unsuitable RNA nucleotide at a base of the DNA, the RNA polymerase remains longer on the corresponding DNA site. This increases the likelihood that the wrong nucleotide RNA removed from the DNA. Overall, an accuracy of one error per 10,000 base pairs is achieved by this mechanism. This corresponds to about one error per synthesized RNA molecule. RNA synthesis occurs in the 5 ' → 3' direction.

Thus the 5 ' end of the DNA corresponding to the 5' end of the mRNA, as well as the N-terminal end of the newly formed protein in the translation ( colinearity ). The same applies to the 3'-end and the C-terminus. Thus, the original DNA - sequence as well as the resulting mRNA sequence read from the 3 'direction into the 5'- direction, and translates into the protein (C-terminal → the N-terminus ).

RNA polymerases do not require a primer, in contrast to DNA polymerases. Escherichia coli, the RNA strand is the RNA polymerase with a rate of about 50 nucleotides per second is increased (17 nm / s).

For the elucidation of the mechanism of transcription by the RNA polymerase of the American chemist Roger D. Kornberg won the 2006 Nobel Prize in Chemistry.