Ribozyme

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Model of a hammerhead ribozyme

Ribozymes (of ribo nucleic acid ( RNA ) and En zym ) are catalytically active RNA molecules, such as enzymes, catalyze chemical reactions.

For this discovery, Sidney Altman and Thomas R. Cech were awarded the Nobel Prize in Chemistry in 1989, as it had been assumed up to this point that only proteins had catalytic activity in the cell . The discovery of ribozymes has far-reaching effects, especially in the area of chemical evolution , as it supports the RNA world hypothesis .

Ribozymes, however, are not uncommon, each cell contains several thousand of them, which differ structurally and can be divided into about a dozen classes. For example, in prokaryotes the 23S rRNA and in eukaryotes the 28S rRNA of the ribosomes catalyzes the formation of the peptide bond during translation ( peptidyl transferase ). The spliceosomes are ribozymes, here the tight network of catalyzed snRNAs the splicing . There are also proteins in both the ribosome and the spliceosome; However, these do not take part in the actual reaction, but merely ensure that the RNA adopts the correct structure for catalysis. There are also ribozymes that have no need of proteins, such as the hammerhead ribozyme , which for example, some viruses use to - to put it vividly - to cut their RNA to the correct length, or selbstspleißende - intron from Tetrahymena thermophila , for whose discovery was awarded the above-mentioned Nobel Prize. Several classes of ribozymes self-cleave into their final functional form .

A whole series of ribozymes was developed in the test tube (mostly via SELEX ), which catalyze various reactions. The main difference between enzymes and ribozymes lies in the speed of the reaction, but not in the variety of catalyzed reactions. The catalysis of a Diels-Alder reaction is particularly interesting , as it could in principle have served in the very early phase of evolution to synthesize the building blocks of RNA so that such an RNA could have replicated itself. It would thus represent an important link between chemical and biological evolution.

literature

  • Sven P. Thoms: Origin of Life. Fischer, Frankfurt 2005 , ISBN 3-596-16128-2
  • Jon R. Lorsch, Jack W. Szostak : In vitro evolution of new ribozymes with polynucleotide kinase activity. In: Nature 371, No. 6492, 1994 , pp. 31-36
  • Thomas R. Cech, Olke C. Uhlenbeck: Hammerhead nailed down. In: Nature 372, No. 6501, 1994 , pp. 39-40
  • B. Alberts, A. Johnson, J. Lewis, M. Raff, K. Roberts, P. Walter: Molecular Biology of the Cell. 4th edition, Wiley-VCH, Weinheim 2004 , ISBN 3-527-30492-4
  • Adam Roth, Zasha Weinberg u. a .: A widespread self-cleaving ribozyme class is revealed by bioinformatics. In: Nature Chemical Biology. 10, 2013, pp. 56-60, doi: 10.1038 / nchembio.1386 .