Detoxifying Gold

After reading “Protection from Poisonous Gold” (C&EN, Feb. 11, page 8), I read with interest the paper “Gold biomineralization by a metallophore from a gold-associated microbe” (Nat. Chem. Biol., DOI: 10.1038/nchembio.1179). I find it highly unlikely that the compound the authors called delftibactin is primarily synthesized as a gold inactivator; rather, it is likely an adventitious property of a standard bacterial iron chelator (siderophore).

This hydroxamate ortho-citrate structure is similar to that of many other siderophores. The hexadentate, all-oxygen donor ligands are characteristic chelators for high-spin ferric ions and closely related compounds (see, for example, BioMetals, DOI: 10.1023/a:1020218608266 or Chem. Rev., DOI: 10.1021/cr9002787).

It is unusual to have an N-formyl hydroxamate (although this is observed in pyoverdins), and it might contribute to activation as a reductant. I suggest that controls be done with N-formyl and N-acetyl hydroxamates to see if they act in a similar fashion for gold detoxification. The excitement about this being a gold metallophore is certainly misplaced.

Kenneth Raymond
Berkeley, Calif.