Organisms have evolved different strategies to seclude certain molecules to specific locations of the cell. This is most pronounced in eukaryotes with their extensive intracellular membrane systems. Intracellular compartmentalization is particularly critical in genome containing organelles, which because of their bacterial evolutionary ancestry still maintain protein-synthesis machinery that resembles more their evolutionary origin than the extant eukaryotic cell they once joined as an endosymbiont. Despite this, it is clear that genome-containing organelles such as the mitochondria are not in isolation and many molecules make it across the mitochondrial membranes from the cytoplasm. In this realm the import of tRNAs and the enzymes that modify them prove most consequential. In this review, we discuss two recent examples of how modifications typically found in cytoplasmic tRNAs affect mitochondrial translation in organisms that forcibly import all their tRNAs from the cytoplasm. In our view, the combination of tRNA import and the compartmentalization of modification enzymes must have played a critical role in the evolution of the organelle. © 2018 IUBMB Life, 70(12):1207-1213, 2018.
- Klíčová slova
- 1-methylguanosine, import, mitochondria, trypanosomes, wybutosine,
- MeSH
- cytoplazma genetika MeSH
- genom mitochondriální genetika MeSH
- intracelulární membrány MeSH
- mitochondriální membrány metabolismus MeSH
- mitochondrie genetika MeSH
- posttranskripční úpravy RNA genetika MeSH
- proteosyntéza genetika MeSH
- RNA transferová genetika MeSH
- symbióza genetika MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
- Research Support, N.I.H., Extramural MeSH
- Názvy látek
- RNA transferová MeSH
The mitochondrial DNA of diplonemid and kinetoplastid protists is known for its suite of bizarre features, including the presence of concatenated circular molecules, extensive trans-splicing and various forms of RNA editing. Here we report on the existence of another remarkable characteristic: hyper-inflated DNA content. We estimated the total amount of mitochondrial DNA in four kinetoplastid species (Trypanosoma brucei, Trypanoplasma borreli, Cryptobia helicis, and Perkinsela sp.) and the diplonemid Diplonema papillatum. Staining with 4',6-diamidino-2-phenylindole and RedDot1 followed by color deconvolution and quantification revealed massive inflation in the total amount of DNA in their organelles. This was further confirmed by electron microscopy. The most extreme case is the ∼260 Mbp of DNA in the mitochondrion of Diplonema, which greatly exceeds that in its nucleus; this is, to our knowledge, the largest amount of DNA described in any organelle. Perkinsela sp. has a total mitochondrial DNA content ~6.6× greater than its nuclear genome. This mass of DNA occupies most of the volume of the Perkinsela cell, despite the fact that it contains only six protein-coding genes. Why so much DNA? We propose that these bloated mitochondrial DNAs accumulated by a ratchet-like process. Despite their excessive nature, the synthesis and maintenance of these mtDNAs must incur a relatively low cost, considering that diplonemids are one of the most ubiquitous and speciose protist groups in the ocean. © 2018 IUBMB Life, 70(12):1267-1274, 2018.
- Klíčová slova
- DNA content, kinetoplast DNA, mitochondrial DNA, protist,
- MeSH
- Euglenozoa genetika MeSH
- fylogeneze MeSH
- Kinetoplastida genetika MeSH
- mitochondriální DNA genetika izolace a purifikace ultrastruktura MeSH
- mitochondrie genetika MeSH
- trans-splicing genetika MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- mitochondriální DNA MeSH
Complex cellular machines and processes are commonly believed to be products of selection, and it is typically understood to be the job of evolutionary biologists to show how selective advantage can account for each step in their origin and subsequent growth in complexity. Here, we describe how complex machines might instead evolve in the absence of positive selection through a process of "presuppression," first termed constructive neutral evolution (CNE) more than a decade ago. If an autonomously functioning cellular component acquires mutations that make it dependent for function on another, pre-existing component or process, and if there are multiple ways in which such dependence may arise, then dependence inevitably will arise and reversal to independence is unlikely. Thus, CNE is a unidirectional evolutionary ratchet leading to complexity, if complexity is equated with the number of components or steps necessary to carry out a cellular process. CNE can explain "functions" that seem to make little sense in terms of cellular economy, like RNA editing or splicing, but it may also contribute to the complexity of machines with clear benefit to the cell, like the ribosome, and to organismal complexity overall. We suggest that CNE-based evolutionary scenarios are in these and other cases less forced than the selectionist or adaptationist narratives that are generally told.
- MeSH
- biologická evoluce * MeSH
- editace RNA MeSH
- fyziologická adaptace MeSH
- genetický drift * MeSH
- lidé MeSH
- modely genetické MeSH
- rostliny anatomie a histologie genetika metabolismus MeSH
- sestřih RNA MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
- MeSH
- biochemie dějiny MeSH
- dějiny 20. století MeSH
- Check Tag
- dějiny 20. století MeSH
- Publikační typ
- biografie MeSH
- časopisecké články MeSH
- historické články MeSH
- portréty MeSH
- Geografické názvy
- Československo MeSH
- Spojené státy americké MeSH
- O autorovi
- Kotyk, Armost
The exchange of mass, energy, and information with the environment typical of open systems can also be found in enzymes. An enzyme is able to receive information on substrate concentration in an arbitrary concentration range. This actually follows from the elementary solution of Michaelis-Menten kinetics. The Michaelis constant can be seen as a relation between the decreasing parameter of a zero-order reaction and the increasing parameter of a first-order reaction over a certain time interval. This excludes the state of zero-order kinetics and consequently the state of zero content of concentration information.
- MeSH
- chemické modely * MeSH
- enzymy chemie metabolismus fyziologie MeSH
- kinetika MeSH
- statistické modely MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- enzymy MeSH
We have searched for the exclusivity of common sequence motifs of the mitochondrial uncoupling proteins (UCP1, UCP2, UCP3, UCP4, BMCP1, and plant UCP [PUMP]) within the gene family of mitochondrial anion carrier proteins. The UCP-specific sequences, "UCP signatures", were found in the first, second, and fourth alpha-helices. First: Ala/Ser-Cys/Thr/n-n/Phe-Ala/Gly-[negatively charged residue]-n/Phe-n/Cys-Thr-Phe/n; second: Gly/Ala-Ile/Leu-Gln/X-[positively charged residue]-NH-n/Cys-Ser/nphi/X-n/Ser-OH/Gly-n-[positively charged residue]-Ile/Met-Gly/Val-n/Thr; fourth: Pro-Asn/ Thr-n-X-[positively charged residue]-Asn/Ser/Ala-n-n-Ile/Leu-n-Asn/Val-Cys/n-n/Thr-[negatively charged residue]-n-n/Thr/Pro-OH/Val (n, nonpolar; phi, aromatic; (positively charged residue/negatively charged residue, charged residue). The second and part of the third signature are also present in the yeast dicarboxylate transporter. The UCP signature excluding BMCP1 was also found in the second matrix segment: [positively charged residue]-(Pro/ del-Leu/del)-[positively charged residue]-phi-X-Gly/Ser-Thr/n-X-NH/[negatively charged residue]-Ala-phi. These UCP signatures are thought to be involved in fatty acid anion binding and translocation.
- MeSH
- aminokyselinové motivy MeSH
- fungální proteiny chemie MeSH
- iontové kanály MeSH
- konzervovaná sekvence MeSH
- křečci praví MeSH
- krysa rodu Rattus MeSH
- lidé MeSH
- membránové proteiny chemie metabolismus MeSH
- membránové transportní proteiny * MeSH
- mitochondriální odpřahující proteiny MeSH
- mitochondriální proteiny * MeSH
- molekulární sekvence - údaje MeSH
- myši MeSH
- proteiny nervové tkáně chemie MeSH
- proteiny chemie MeSH
- rostlinné proteiny chemie MeSH
- sbalování proteinů MeSH
- sekundární struktura proteinů MeSH
- sekvence aminokyselin MeSH
- sekvenční homologie aminokyselin MeSH
- skot MeSH
- terciární struktura proteinů MeSH
- transportní proteiny mitochondriální membrány MeSH
- transportní proteiny chemie metabolismus MeSH
- uncoupling protein 1 MeSH
- uncoupling protein 2 MeSH
- vazebná místa MeSH
- zvířata MeSH
- Check Tag
- křečci praví MeSH
- krysa rodu Rattus MeSH
- lidé MeSH
- myši MeSH
- skot MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- fungální proteiny MeSH
- iontové kanály MeSH
- membránové proteiny MeSH
- membránové transportní proteiny * MeSH
- mitochondriální odpřahující proteiny MeSH
- mitochondriální proteiny * MeSH
- proteiny nervové tkáně MeSH
- proteiny MeSH
- rostlinné proteiny MeSH
- SLC25A14 protein, human MeSH Prohlížeč
- Slc25a14 protein, mouse MeSH Prohlížeč
- Slc25a14 protein, rat MeSH Prohlížeč
- transportní proteiny mitochondriální membrány MeSH
- transportní proteiny MeSH
- UCP1 protein, human MeSH Prohlížeč
- Ucp1 protein, mouse MeSH Prohlížeč
- Ucp1 protein, rat MeSH Prohlížeč
- UCP2 protein, human MeSH Prohlížeč
- Ucp2 protein, mouse MeSH Prohlížeč
- Ucp2 protein, rat MeSH Prohlížeč
- uncoupling protein 1 MeSH
- uncoupling protein 2 MeSH
