Ribocyte

from Wikipedia, the free encyclopedia

Ribocytes (English: Ribocytes, also: Ribocells) are hypothetical primitive precursors of today's living beings, which are based on ribonucleic acid (RNA) and represent a central component of the RNA world hypothesis . In these living beings, RNA takes on both the function of storing information, which is performed by deoxyribonucleic acids (DNA) in today's organisms , and the function of catalysis of chemical reactions, for which proteins are responsible in today's organisms . The hypothetical existence and evolution of ribocytes can be described using the quasi-species model .

properties

One of the basic characteristics that allow the existence of living beings as Ribozyten, the ability to reproduce (including replication ) and translation ( translation ) of their genetic information as well as the presence of at least primitive metabolism. With the discovery that the ribosomal RNA of the eyelash animal Tetrahymena can splice itself, the enzymatic properties of ribonucleic acids ( ribozymes ) were verified for the first time in 1982 . In addition, RNA molecules have been discovered that produce important components of cell metabolism, including their own building blocks, and even those that are capable of replication. Based on experimental data with ribozymes, it is assumed that biochemical processes in ribocytes proceed significantly more slowly than in "modern" cells.

A demarcation from the environment, like a cell membrane , is an important achievement of ribocytes and a prerequisite for their further evolution. It is assumed that at least part of the ribocyte RNA was directly or indirectly connected to the cell membrane in order to control elementary cell functions such as the transport of substances through the cell membrane and the shape of the cell.

Further development to the DNA world

The organization of DNA, its replication and transcription in RNA, happens very differently in today's living beings (cellular organisms). There are two groups: on the one hand there are the bacteria , on the other hand the archaea and the eukaryotes ( presumably derived from them) (the latter characterized by a complex structure with a delimited cell nucleus ). These differences have recently turned out to be so great that it is now assumed that both groups developed the function of DNA as the carrier of genetic information. The DNA genome does not seem to have any homology in today's living world ; the DNA world would be polyphyletic . The primordial cellular RNA organisms (ribocytes) could have acquired the ability to use DNA as a carrier of genetic information several times from (DNA) viruses . This view of the transition from the RNA to the DNA world is called the out-of-virus hypothesis . The function of the ribosomes was then completely or largely restricted to protein synthesis.

Individual evidence

  1. ↑ Schuster, P .; Eigen, M .: The hypercycle, a principle of natural self-organization . Springer-Verlag, Berlin 1979, ISBN 0-387-09293-5 .
  2. ↑ P. Forterre, M. Krupovic: The Origin of the virion and Virocells: The Escape Hypothesis Revisited . In: Viruses: Essential Agents of Life, pp. 43-60, Springer Link, September 25, 2012, ISBN 978-94-007-4898-9 .
  3. ↑ Kruger K, Grabowski PJ, Zaug AJ, Sands J, Gottschling DE, Cech TR: Self-splicing RNA: autoexcision and autocyclization of the ribosomal RNA intervening sequence of Tetrahymena . In: Cell . 31, No. 1, November 1982, pp. 147-57. PMID 6297745 .
  4. ↑ Unrau PJ, Bartel DP: RNA-catalysed nucleotide synthesis . In: Nature . 395, No. 6699, September 1998, pp. 260-3. doi : 10.1038 / 26193 . PMID 9751052 .
  5. ^ Johnston WK, Unrau PJ, Lawrence MS, Glasner ME, Bartel DP: RNA-catalyzed RNA polymerization: accurate and general RNA-templated primer extension . In: Science . 292, No. 5520, May 2001, pp. 1319-25. doi : 10.1126 / science.1060786 . PMID 11358999 .
  6. ↑ Lincoln TA, Joyce GF : Self-sustained replication of an RNA enzyme . In: Science . 323, No. 5918, February 2009, pp. 1229-32. doi : 10.1126 / science.1167856 . PMID 19131595 . PMC 2652413 (free full text).
  7. ^ Szostak JW, Bartel DP, Luisi PL: Synthesizing life . In: Nature . 409, No. 6818, January 2001, pp. 387-90. doi : 10.1038 / 35053176 . PMID 11201752 .
  8. ↑ Joseph F. Sutherland: on The Origin Of Tha Bacteria And The Archaea , on BC of August 16, 2014
  9. ↑ Forterre, Patrick : Evolution - The true nature of viruses , in: Spectrum August 2017, p. 37 (online article from July 19, 2017)

literature