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— Distortion of the protein
Another nail in the coffin of the arsenic life story has been published suggesting that GFAJ-1 does not in fact metabolise arsenate, but instead is very good at distinguishing the poison from phosphate. Earlier this year, two papers found that despite earlier claims, the bacterium did not in fact take up arsenate, the new paper explains in more detail why.
Publishing in Nature, Dan Tawfik and colleagues decided to investigate how exactly GFAJ-1, and other bacteria that live in arsenic rich environments, survive. Can they distinguish between the two anions, and if so, how?
The trick, suggests Tawfik, is in the peristaltic phosphate binding proteins which are highly tuned in GFAJ-1. Although arsenate ions are only a little larger than phosphate, that size difference is enough to distort a low energy hydrogen bond and stop arsenate uptake (see left).
I can’t help but wonder, have we finally laid this to rest, or will more papers refuting GFAJ-1′s ability to metabolise arsenate keep coming out for a while yet? If they keep getting their authors in high impact journals, you can see why anyone working on applicable research might want to join in.