ATP as the Energy Carrier
Location: Outside U.S.
Date: Fall 2012
Why ATP has been chosen as the main energy carrier, and not other trinucleotide phosphates such as GTP?
ATP is the major energy carrier. However, there are other energy
carriers such as GTP, cAMP, and UTP. I do not know of a specific
reason why ATP is chosen over the others. Perhaps adenosine is more
common than guanosine or uridine in the "primordial soup" (as it is
However, if you find someone who knows this, please let me know.
This is an interesting question without a clear answer. Certainly it
is true that ATP is the major 'unit of currency' for energy in the
cell to the exclusion of other naturally occurring nucleoside
triphosphates such as GTP, CTP, and UTP. That being said, other
nucleoside triphosphates do carry out important roles in the cell.
Notably, GTP act much like ATP as an energy carrier during the
activation of G protein coupled receptors (which, incidentally, was
the subject of this year's Nobel Prize in Chemistry). GTP is also a
part of the citric acid cycle, where glucose is broken down for
energy. Other nucleoside triphosphates have more obscure by not
unimportant roles as coenzymes in metabolic reactions much like ATP.
Of course, it is still certainly true that ATP is by far the most
common carrier of energy in the cell, and is involved in a much wider
array of metabolic and signalling reactions in the cell. Answering
the question of 'why' is a bit trickier. It makes sense from an
evolutionary perspective that one nucleoside triphosphate would become
the dominant molecule; after all, it allows for structural similarity
between a wide variety of proteins that utilize ATP for energy. I do
not believe, though, that we know why ATP was the specific molecule
that ended up being this common energy carrier rather than a different
nucleoside. It may indeed be random chance - any nucleoside could
have worked, but ATP was the first one that evolved, and it quickly
became the dominant energy 'currency' by copying its functionality to
other proteins. It is possible, though, that there is some unknown
selective advantage to using ATP over other nucleoside triphosphates.
S. Unterman Ph.D.
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Update: November 2011