Evolution bacterial cytochromes

We find also some interesting results from the data shown in Table 3.4. Comparing the amino acid sequence of cytochrome c from N. winogradskyi with those of cytochromes c from human, monkey, and tuna, the numbers of the different amino acids at the corresponding positions of the sequence are found to be 62, 61, and 59, respectively. The number of different amino acids in the sequence is 72 between yeast and the bacterial cytochrome c. From these data, the evolutionary distance between yeast and the bacterium is farther than that between the animals and the bacterium. The number of different amino acids in the sequence of cytochrome c is 44 between human and yeast cytochromes c. By simple analysis of the figures, we are led to a conclusion that the bacterium has appeared on Earth evolutionarily after human or that yeast has appeared after human. This is a mystery of molecular evolution that needs to be solved in future studies. 

Nonetheless, photosynthesis did not evolve immediately at the origin of life. The failure to discover photosynthesis in the domain of Archaea implies that photosynthesis evolved exclusively in the domain of Bacteria. Eukaryotes appropriated through endosymbiosis the basic photosynthetic units that were the products of bacterial evolution. All domains of life do have electron-transport chains in common, however. As we have seen, components such as the ubiquinone-cytochrome c oxidoreductase and cytochrome hf family are present in both respiratory and photosynthetic electron-transport chains. These components were the foundations on which light-energy-capturing systems evolved. 

In the spirit that a distorted picture is better than no picture at all, we should like to close the chapter with a few suggestive ideas on bacterial evolution which have come from the cytochrome study. They are offered less as dogma than as useful targets for future discussion ... 

In spite of recent progress toward elucidation of the mechanism of nuclear envelope formation In modern eukaryotes, evolutionary origins of the eukaryote nucleus remain obscure. Even the concept of nuclear envelope organization around annulae derived from preexisting annulae offers little to help select among the various possibilities. Yet, similarities of Inner membrane of the nuclear envelope and the procaryotic cell membrane argue for a common parallel evolution of these two membrane types. For example, the Inner nuclear membrane Is associated with DNA (i) and perhaps even with DNA replication 21, 23) as In bacterial cells (J). There was even a report that It contained cytochrome oxidase 20), an enzyme associated with the plasma membrane of prokaryotes and critical to the development of aerobic metabolism. 

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