Abstract
Abstract The data presented and discussed in this report summarize evidence showing that ribosomes isolated from several eucaryotic (plant and animal) organisms exhibit ample variations of the composition of their protein moiety and that the degree of dissimilarity correlates with the degree of taxonomic kinship of the organisms from which the ribosomes were derived. They also provide evidence that (a) the 80-S ribosomes isolated from the cytoplasmic matrix of higher plants and yeast and the 70-S ribosomes derived from both chloroplasts and mitochondria are endowed with highly dissimilar protein complements, (b) the organellar (67-S) ribosomes derived from the chloroplasts of more or less distantly related plants exhibit a greater degree of dissimilarity than the corresponding 78-S ribosomes derived from the extra-chloroplast, extramitochondrial portion of the cytoplasm, i.e., in distant organisms the protein composition of cytoplasmic ribosomes tends to be more congruent than that of organellar ribosomes. Furthermore, it is shown that the 67-S and the 78-S ribosomes of higher plants resemble respectively those of E. Coli and of animal tissues for (a) the presence or the absence of acidic proteins and (b) the mode of distribution of their constituent proteins between the two derived ribosomal subunits. Calculations based on the coding potential of a haploid plastid genome (Euglena gracilis) support the contention that the structural proteins of the organellar (chloroplastic) ribosomes are coded for by the plastid DNA, if it is assumed that one plastid contains three monomer genomes of 0.9×109 daltons each, and that each chloroplast ribosome contains 50 different kinds of ribosomal proteins of 2.4×104 daltons each. The possibility is discussed that the great degree of dissimilarity among organellar ribosomes in distantly related organisms is accounted for by the greater evolutionary versatility of the plastid genome as compared to the principal genome. It is postulated that in extant organisms the observed heterogeneity of both the 70-S and the 80-S ribosomes has resulted from the evolutionary suppression of mutations leading to ambiguity by concurrent mutations restoring ribosome fidelity, by mechanisms similar in principle to the suppression of RAM (ribosomal ambiguity mutations) mutations by intervening « restrictive » mutations in E. Coli cells.
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Claims 6
Claim · model-written summary
Ribosomal protein composition varies among eukaryotic organisms and dissimilarity correlates with taxonomic distance.
Not reportedDirection
Verbatim
e0“ribosomes isolated from several eucaryotic (plant and animal) organisms exhibit ample variations of the composition of their protein moiety and that the degree of dissimilarity correlates with the degree of taxonomic kinship of the organisms”
Claim · model-written summary
Plant cytoplasmic and organellar ribosomes have highly dissimilar protein complements.
- Taxon
- higher plantsEmbryophytae0
- Outcome
- highly dissimilar protein complementse0
Not reportedDirection
Verbatim
e0“the 80-S ribosomes isolated from the cytoplasmic matrix of higher plants and yeast and the 70-S ribosomes derived from both chloroplasts and mitochondria are endowed with highly dissimilar protein complements”
Claim · model-written summary
Chloroplast ribosomes differ more among distantly related plants than cytoplasmic ribosomes.
- Taxon
- plantsViridiplantaee0
- Outcome
- degree of dissimilaritye0
- Direction
- greatere0
- Comparator
- corresponding 78-S ribosomese0
Verbatim
e0“the organellar (67-S) ribosomes derived from the chloroplasts of more or less distantly related plants exhibit a greater degree of dissimilarity than the corresponding 78-S ribosomes derived from the extra-chloroplast, extramitochondrial portion of the cytoplasm”
Claim · model-written summary
Higher plant organellar and cytoplasmic ribosomes resemble bacterial and animal ribosomes respectively in acidic proteins and protein distribution between subunits.
- Taxon
- higher plantsEmbryophytae0
- Outcome
- presence or the absence of acidic proteins and (b) the mode of distribution of their constituent proteinse0
Not reportedDirection
Verbatim
e0“the 67-S and the 78-S ribosomes of higher plants resemble respectively those of E. Coli and of animal tissues for (a) the presence or the absence of acidic proteins and (b) the mode of distribution of their constituent proteins between the two derived ribosomal subunits”
Claim · model-written summary
Plastid genome coding calculations support plastid DNA encoding chloroplast ribosomal structural proteins under stated assumptions.
- Taxon
- Euglena gracilisEuglena gracilise0
- Gene
- plastid DNAe0
- Outcome
- structural proteins of the organellar (chloroplastic) ribosomes are coded for by the plastid DNAe0
- Qualifier
- if it is assumed that one plastid contains three monomer genomes of 0.9×109 daltons eache0
Not reportedDirection
Verbatim
e0“Calculations based on the coding potential of a haploid plastid genome (Euglena gracilis) support the contention that the structural proteins of the organellar (chloroplastic) ribosomes are coded for by the plastid DNA, if it is assumed that one plastid contains three monomer genomes of 0.9×109 daltons each, and that each chloroplast ribosome contains 50 different kinds of ribosomal proteins of 2.4×104 daltons each”
Claim · model-written summary
The authors postulate ribosome heterogeneity arose through mutations restoring fidelity.
- Taxon
- extant organismse0
- Outcome
- observed heterogeneity of both the 70-S and the 80-S ribosomese0
- Qualifier
- concurrent mutations restoring ribosome fidelitye0
Not reportedDirection
Verbatim
e0“in extant organisms the observed heterogeneity of both the 70-S and the 80-S ribosomes has resulted from the evolutionary suppression of mutations leading to ambiguity by concurrent mutations restoring ribosome fidelity”