Mitosome

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Mitosomes are organelles found in some unicellular , anaerobic, or microaerophilic eukaryotic organisms; an outdated name for mitosome is crypton . It is almost certainly a question of severely degenerated mitochondria that have lost the ability to oxidative phosphorylation . Since they have only recently been discovered, they are not yet well studied. A previous report suggested the presence of DNA in these organelles in Entamoeba histolytica , but more recent research has disproved this in this species.

General

Mitosomes are only found in unicellular eukaryotes that do not have mitochondria. They were first found in Entamoeba histolytica , the cause of amoebic dysentery . Later they were also z. B. found in microsporidia such as Encephalitozoon cuniculi and Trachipleistophora hominis . In the beginning they were also called Crypton, but this name did not catch on.

construction

Mitosomes, like mitochondria, have a double membrane . In contrast to the mitochondrial membrane, however, no potential difference could be determined between the intermembrane space and the matrix . Despite in situ nick translation and antibody staining, no DNA could be detected in the mitosomes . This revised older reports that reported DNA-containing mitosomes. Furthermore, proteins could be detected which are related to the translocase of the inner mitochondrial membrane and the presequence protease . In Trachipleistophora, 7–47 mitosomes per cell were found by immunogold labeling and electron microscopy , with a size of approx. 50X90nm only one tenth the size of mitochondria.

function

Mitosomes are not capable of oxidative phosphorylation, the main task of mitochondria. Living beings with mitosomes can therefore not obtain ATP from the chemical energy of their food via the respiratory chain . Therefore, mitosomes are so far only known from eukaryotes that occur under oxygen-free or oxygen-poor conditions, where the oxygen for oxidative phosphorylation is already missing. Experiments on yeast show that mitosomes play a role in the biosynthesis of iron-sulfur clusters : If the respective proteins were replaced by the corresponding proteins from mitosomes, an Fe-S cluster biosynthesis continued. In addition, antibody markings showed that Fe-S cluster synthesis takes place in the mitosomes. The proteins responsible include frataxin , cysteine ​​desulfurase , Isu1 and mitochondrial Hsp70 . Since Fe-S proteins assume indispensable functions, this exerts a strong selection pressure to preserve the mitosomes. Important Fe-S proteins in amitochondrial eukaryotes are z. B. ferredoxin , hydrogenases or pyruvate ferredoxin oxidoreductase.

origin

It can be said with reasonable certainty that mitosomes are severely reduced mitochondria. This is indicated, among other things, by the fact that mitosomes have Cpn60 and Hsp70, which are responsible for the folding of proteins imported into the mitosome and are derived from mitochondrial proteins. In addition, proteins that are imported into mitosomes have a signal sequence that enables them to enter the mitochondrion or hydrogenosome when expressed in a corresponding organism . The investigation of 5 related species of Entamoeba also shows that these proteins are derived from common ancestors and not obtained by lateral gene transfer from other organisms.

Together with the hydrogenosomes, mitochondria and mitosomes are therefore classified as " mitochondrion-related organelles" ( English mitochondrion-related organelles , MROs). These also include the anaerobic and DNA- free organelles of Henneguya salminicola (alias H. zschokkei , Myxozoa )

Others

Since microsporidia do not have mitochondria, it was assumed that they are basal eukaryotes that split off from the remaining eukaryotes before the endosymbiosis of the mitochondria. It was not until the late 1990s that this picture changed with the discovery of mitosomes, so that today they are placed close to mushrooms .

The hydrogenosome is another organelle that was formed from mitochondria through reduction and enables fermentation under anaerobic and aerobic conditions. Like mitosomes, hydrogenosomes have completely lost their DNA. The only exception is the ciliate Nyctotherus ovalis , which thus a missing link is between the mitochondrion and hydrogenosome.

See also

Individual evidence

  1. ↑ a b c d Andrew J. Roger, Jeffrey D. Silberman: Cell evolution. Mitochondria in hiding . In: Nature . tape 418 , no. 6900 , August 22, 2002, p. 827-829 , doi : 10.1038 / 418827a , PMID 12192393 .
  2. ↑ a b c Sudip Ghosh, Jessica Field, Rick Rogers, Mark Hickman, John Samuelson; WA Petri Jr. (Ed.): The "Entamoeba histolytica" Mitochondrion-Derived Organelle (Crypton) Contains Double-Stranded DNA and Appears To Be Bound by a Double Membrane . in: Infection and Immunity, 2000 Jul; 68 (7): pp. 4319-4322, PMID 10858251 ; doi: 10.1128 / IAI.68.7.4319-4322.2000 , PMC 101756 (free full text)
  3. ^ A b J. Tovar, A. Fischer, CG Clark: The mitosome, a novel organelle related to mitochondria in the amitochondrial parasite Entamoeba histolytica. In: Molecular microbiology. Volume 32, Number 5, June 1999, pp. 1013-1021, PMID 10361303 .
  4. ↑ a b c Gloria León-Avila, Jorge Tovar: Mitosomes of Entamoeba histolytica are abundant mitochondrion-related remnant organelles that lack a detectable organellar genome . In: Microbiology (Reading, England) . tape 150 , Pt 5, May 2004, p. 1245-1250 , doi : 10.1099 / mic.0.26923-0 , PMID 15133087 .
  5. ^ BA Williams, RP Hirt, JM Lucocq, TM Embley: A mitochondrial remnant in the microsporidian Trachipleistophora hominis. In: Nature. Volume 418, number 6900, August 2002, pp. 865-869, doi: 10.1038 / nature00949 . PMID 12192407 .
  6. ↑ a b Pavel Dolezal, Ondrej Smíd, Petr Rada, Zuzana Zubácová, Dejan Bursać, Robert Suták, Jana Nebesárová, Trevor Lithgow, Jan Tachezy: Giardia mitosomes and trichomonad hydrogenosomes share a common mode of protein targeting . In: Proceedings of the National Academy of Sciences . tape 102 , no. 31 , August 2, 2005, pp. 10924-10929 , doi : 10.1073 / pnas.0500349102 , PMID 16040811 , PMC 1182405 (free full text).
  7. ^ AV Goldberg, S. Molik, AD Tsaousis, K. Neumann, G. Kuhnke, F. Delbac, CP Vivares, RP Hirt, R. Lill, TM Embley: Localization and functionality of microsporidian iron-sulfur cluster assembly proteins. In: Nature. Volume 452, number 7187, April 2008, pp. 624-628, doi: 10.1038 / nature06606 . PMID 18311129 .
  8. ^ J. Tovar, G. León-Avila, LB Sánchez, R. Sutak, J. Tachezy, M. van der Giezen, M. Hernández, M. Müller, JM Lucocq: Mitochondrial remnant organelles of Giardia function in iron-sulfur protein maturation. In: Nature. Volume 426, number 6963, November 2003, ISSN  1476-4687 , pp. 172-176, doi: 10.1038 / nature01945 . PMID 14614504 .
  9. ↑ a b Christina Bakatselou, Dany Beste, Ayodeji O. Kadri, Sushela Somanath, C. Graham Clark: Analysis of genes of mitochondrial origin in the genus Entamoeba . In: The Journal of Eukaryotic Microbiology . tape 50 , no. 3 , June 1, 2003, p. 210-214 , doi : 10.1111 / j.1550-7408.2003.tb00119.x , PMID 12836878 .
  10. ↑ Jan Osterkamp: First animal without breathing and mitochondria , on: Spektrum.de from February 25, 2020
  11. ↑ Tel Aviv University researchers discover unique non-oxygen breathing animal , on: EurekAlert! from February 25, 2020
  12. ↑ See also: H. nuesslini ; Peacock Wrasse§ Threats ( H. tunisiensis )
  13. ↑ Brigitte Boxma, Rob M. de Graaf, Georg WM van der Staay, Theo A. van Alen, Guenola Ricard, Toni Gabaldon, Angela HAM van Hoek, Seung Yeo Moon-van der Staay, Werner JH Koopman, Jaap J. van Hellemond , Aloysius GM Tielens, Thorsten Friedrich, Marten Veenhuis, Martijn A. Huynen, Johannes HP Hackstein: An anaerobic mitochondrion that produces hydrogen . In: Nature . tape 434 , no. 7029 , February 3, 2005, p. 74-79 , doi : 10.1038 / nature03343 .
  14. ↑ A. Akhmanove et al .: A hydrogenosomes with a genome . In: Nature . tape 396 , no. 6711 , December 10, 1998, p. 527-528 , doi : 10.1038 / 25023 ( nature.com ).