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Name: Niloufar
Status: student
Grade: other
Location: Outside U.S.
Country: Iran
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 often called).

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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