The hydrogen hypothesis for the first eukaryote

Martin, William; Müller, Miklós

doi:10.1038/32096

Cited by 1,123 publications

(979 citation statements)

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“…It remains a matter of discussion as to how and why mitochondria were initially acquired [38,39], but the ongoing driver for evolution of mitochondria would be the generation of ATP by mitochondria and its supply to the host cytosol [39]. This export would require insertion of a novel and primitive ADP/ATP carrier (AAC) into the inner membrane of the 'protomitochondrion'.…”

Section: The Protein Import Machinery In Trypanosoma Bruceimentioning

confidence: 99%

The direct route: a simplified pathway for protein import into the mitochondrion of trypanosomes

Schneider

Bursać

Lithgow

2008

Trends in Cell Biology

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Section: The Protein Import Machinery In Trypanosoma Bruceimentioning

confidence: 99%

The direct route: a simplified pathway for protein import into the mitochondrion of trypanosomes

Schneider

Bursać

Lithgow

2008

Trends in Cell Biology

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“…Alternatively, a number of groups have proposed that early evolution involved only two lines, bacteria and archaea, and that the eukaryotic line began with the acquisition of a bacterial endosymbiont by an archaeon. (22) There are a number of variations of this theory. (23) A third proposal is that early evolution involved only one line, bacteria, and that archaea and eukarya separated from the bacterial line relatively recently.…”

Section: Evolution Of Eukaryotesmentioning

confidence: 99%

Evolution of the cytoskeleton

2007

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SummaryThe eukaryotic cytoskeleton appears to have evolved from ancestral precursors related to prokaryotic FtsZ and MreB. FtsZ and MreB show 40−50% sequence identity across different bacterial and archaeal species. Here I suggest that this represents the limit of divergence that is consistent with maintaining their functions for cytokinesis and cell shape. Previous analyses have noted that tubulin and actin are highly conserved across eukaryotic species, but so divergent from their prokaryotic relatives as to be hardly recognizable from sequence comparisons. One suggestion for this extreme divergence of tubulin and actin is that it occurred as they evolved very different functions from FtsZ and MreB. I will present new arguments favoring this suggestion, and speculate on pathways. Moreover, the extreme conservation of tubulin and actin across eukaryotic species is not due to an intrinsic lack of variability, but is attributed to their acquisition of elaborate mechanisms for assembly dynamics and their interactions with multiple motor and binding proteins. A new structure-based sequence alignment identifies amino acids that are conserved from FtsZ to tubulins. The highly conserved amino acids are not those forming the subunit core or protofilament interface, but those involved in binding and hydrolysis of GTP. Historical introduction Discoveries of the prokaryotic cytoskeletonBefore 1990, the cytoskeleton was thought to have evolved only in eukaryotes. Relatives or homologs of actin, tubulin or intermediate filaments were unknown in bacteria or archaea. There were sporadic reports of candidates for bacterial actin and tubulin in the 1970s and 1980s but, apart from some intriguing images of microtubules in certain bacteria,(1) these turned out to be wrong and/or were not followed up.The first suggestions of a bacterial homolog of tubulin appeared in 1992. Three groups independently discovered that the bacterial cell division protein FtsZ bound and hydrolyzed GTP, as does tubulin, and had a seven-amino-acid sequence, GGGTGTG, virtually identical to the "tubulin signature sequence".(2-4) Mukherjee and Lutkenhaus(37) then extended the sequence alignment to find a dozen additional amino acids that were completely conserved in FtsZ and in α, β and γ tubulins. They also showed that FtsZ assembled in vitro into filamentous structures. Erickson et al. (5) found that FtsZ assembled into protofilaments that could adopt two conformations, straight and curved, similar to the straight protofilaments of the microtubule wall and the tubulin rings that peel away from microtubules during disassembly. Any question of homology was resolved when tubulin and FtsZ were found to have virtually identical structures at the level of protein folding.(6,7)If one looks for bacterial relatives of tubulin or actin using a simple computer search for sequence similarity, nothing will be found. In 1992 Bork et al.(8) used a sophisticated structurebased sequence alignment, and they discovered that bacteria did have genes related to actin. Actin is...

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“…This has been called the "Hydrogen Hypothesis" [34]. A bacterial cell metabolized organic compounds to H 2 and CO 2 , and a second species converted those products into CH 4 .…”

Section: Methanogenic Syntrophy (Fig 5)mentioning

confidence: 99%

Metabolic integration during the evolutionary origin of mitochondria

Searcy

2003

Cell Res

115

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Although mitochondria provide eukaryotic cells with certain metabolic advantages, in other ways they may be disadvantageous. For example, mitochondria produce reactive oxygen species that damage both nucleocytoplasm and mitochondria, resulting in mutations, diseases, and aging. The relationship of mitochondria to the cytoplasm is best understood in the context of evolutionary history. Although it is clear that mitochondria evolved from symbiotic bacteria, the exact nature of the initial symbiosis is a matter of continuing debate. The exchange of nutrients between host and symbiont may have differed from that between the cytoplasm and mitochondria in modern cells. Speculations about the initial relationships include the following.(1) The pre-mitochondrion may have been an invasive, parasitic bacterium. The host did not benefit. (2) The relationship was a nutritional syntrophy based upon transfer of organic acids from host to symbiont. (3) The relationship was a syntrophy based upon H2 transfer from symbiont to host, where the host was a methanogen. (4) There was a syntrophy based upon reciprocal exchange of sulfur compounds. The last conjecture receives support from our detection in eukaryotic cells of substantial H2S-oxidizing activity in mitochondria, and sulfur-reducing activity in the cytoplasm.

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The hydrogen hypothesis for the first eukaryote

Cited by 1,123 publications

References 45 publications

The direct route: a simplified pathway for protein import into the mitochondrion of trypanosomes

The direct route: a simplified pathway for protein import into the mitochondrion of trypanosomes

Evolution of the cytoskeleton

Metabolic integration during the evolutionary origin of mitochondria

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