RNA polymerase

as RNA polymerase n one designates enzymes, which catalyze the synthesis of Ribonucleinsäure molecules (RNA ) to the DNA or to the RNA by Transkription.

With Prokaryonten there is only one form of the RNA polymerase.

With Eukaryoten one differentiates three formsthe RNA polymerase:

  1. the RNA polymerase I, those the education of rRNA as pre rRNA (45S prozessiert to 18S; 5.8S; 28S) and some snRNAs (small nuclear RNA) in the nucleolus catalyzes,
  2. which RNA polymerase II, which catalyzes the formation of most mRNA, and
  3. whichRNA polymerase III, which catalyzes the education of tRNA , 7SL-RNA and 5S rRNA.

These RNA polymerases are DNA dependent.

The RNA polymerases are very complex compound. With the yeast ten are different Polypeptid - chains, for whose molecular mass between 7.700 and 140.000 Dalton are appropriate, magnesium, Zinc and two DNA chains take part. Altogether this RNA polymerase exists out over 28.000 atoms.

RNA polymerases have a simple mechanism for error recognition: If to a cousin of the DNA a mismatching RNA Nucleotid deposits itself, then the RNA polymerase remains longer at the appropriateDNA place. By the fact the probability grows that the wrong RNA Nucleotid departs again from the DNA. Altogether by this mechanism an accuracy is reached by an error on 10.000 base pairings. This corresponds for instance to an error per synthesized RNA molecule.

RNA polymerases do not needPrimer. With E. coli the RNA strand becomes by the RNA polymerase with a rate of approx. 50 nucleotides per second (17nm/s) increases.

The RNA synthesis takes place in 5 ' - 3 ' direction.

See also: Genetics - genetic code - protein biosynthesis

 

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