biochemistry - Does GFAJ-1 use Adenosine triarsenate as its energy currency?

This is a cool topic/question.

To answer your question. The hypothesis was based on the conjecture that there was so little phosphorus in the culture medium that phosphorous would have been replaced by arsenic in all its roles in the cell. IF they had found arsenate DNA, it would have been derived from NTAs (nucleotide tri-arsenates) or a hybrid Phosphorous/Arsenic analog of the compound as DNA polymerase consumes NTPs to create DNA. If there were only NTAs to drive DNA biosynthesis, then the cell's energy cycle would also have had to use ATA.

BUT

The primary evidence was that the mono lake strain grew in a fermentor (culture) with lots of arsenic (which is impressive) and very little phosphorous. how little? 3 micromolar. The investigators say that they did add a little phosphorus (3-5 micromolar), which, after some more careful accounting, appears to be enough to keep the bacteria growing at the observed rate without using arsenate nucleotides (submitted to Science).

This is not completely surprising as the original publication in 2010 of a preliminary finding in Science Express which only had x-ray abosorbtion fine edge spectroscopy work consistant with an arsenate like that found in a phosphorus backbone. Given that they did not produce a more direct reading of the compounds such as mass spec or an NMR experiment, this looked pretty iffy in the first place.

You an see why arsenic life was so improbable - a dozen (or more) vital pathways in the cell would have to adapt to use NTAs - pretty much all at once. If they had I suspect Mono lake would be full of those suckers.

Its sort of a bummer, for those of us who want to discover new forms of life, but you can't find what isn't there.