It's a cliche that the oldest deepest divide in life is between bacteria and archaea, but if you assume that it happened in an alkaline hydro-thermal vent (or at least someplace with natural proton gradients), we might have an answer.
One of the most enlightening parts of Nick Lane's "The Vital Question" (coming out in North America on July 20) is explaining the most elegant reason to date for that split, based on these two papers and yes he was a coauthor.
http://rstb.royalsocietypublishing.o.../1622/20130088
http://ift.tt/1IBcdOQ
The second one came later and I agree with David Marjanović posting at
http://ift.tt/1IBcfGq
that it states the premise more clearly. Lane was undoubtedly already writing "The Vital Question" and uses diagrams from the latter paper in the book.
In short, LUCA developed a simple single protein Proton/Sodium antiporter which is still part of the energy converting hydrogenase (Ech) and Complex I of the respiratory chain. It should be called hydronium/Sodium antiporter because hydronium is a cation that forms from water in the presence of hydrogen ions and is nearly identical (115pm vs 117pm) in size to a Sodium ion and allows the antiporter to be indiscriminate. After this event, pumping Sodium ions using the existing proton gradient become advantageous. This led towards a tight modern membrane rather the leaky early one and more sophisticated pumping mechanisms.
From page 151 of the book:
"Yet the similarities and differences begin to make sense if we assume that LUCA did indeed depend on natural proton gradients. If so, the key to pumping could lie in the direction of proton flux through Ech - whether the natural flow of protons into the cell drives carbon fixation, or whether this flux is reversed, with the protein now acting as a membrane pump, pumping protons out of the cell."
The papers say much the same but not as clearly to a layman. :) As Lane says, it was a binary "choice" made by two lines of descendants. One became acetogens and other bacteria and the other became methanogens and other archaea, and much much later they merged to become Eukaryotes that led to us.
Yes, yes this has not yet become the consensus view, but it is slowly growing in adherents.
One of the most enlightening parts of Nick Lane's "The Vital Question" (coming out in North America on July 20) is explaining the most elegant reason to date for that split, based on these two papers and yes he was a coauthor.
http://rstb.royalsocietypublishing.o.../1622/20130088
http://ift.tt/1IBcdOQ
The second one came later and I agree with David Marjanović posting at
http://ift.tt/1IBcfGq
that it states the premise more clearly. Lane was undoubtedly already writing "The Vital Question" and uses diagrams from the latter paper in the book.
In short, LUCA developed a simple single protein Proton/Sodium antiporter which is still part of the energy converting hydrogenase (Ech) and Complex I of the respiratory chain. It should be called hydronium/Sodium antiporter because hydronium is a cation that forms from water in the presence of hydrogen ions and is nearly identical (115pm vs 117pm) in size to a Sodium ion and allows the antiporter to be indiscriminate. After this event, pumping Sodium ions using the existing proton gradient become advantageous. This led towards a tight modern membrane rather the leaky early one and more sophisticated pumping mechanisms.
From page 151 of the book:
"Yet the similarities and differences begin to make sense if we assume that LUCA did indeed depend on natural proton gradients. If so, the key to pumping could lie in the direction of proton flux through Ech - whether the natural flow of protons into the cell drives carbon fixation, or whether this flux is reversed, with the protein now acting as a membrane pump, pumping protons out of the cell."
The papers say much the same but not as clearly to a layman. :) As Lane says, it was a binary "choice" made by two lines of descendants. One became acetogens and other bacteria and the other became methanogens and other archaea, and much much later they merged to become Eukaryotes that led to us.
Yes, yes this has not yet become the consensus view, but it is slowly growing in adherents.
via International Skeptics Forum http://ift.tt/1IBcdOS
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