Zinc-containing ferredoxin from Acidianus ambivalens

A small protein from a hot-spring archaeon with seven iron atoms in two clusters, plus a zinc, all intact.

Explore in 3D

Ferredoxins are small proteins that ferry electrons around the cell. This one comes from Acidianus ambivalens, an archaeon that lives in hot, acidic volcanic springs. It carries seven iron atoms in two iron–sulfur clusters, a [3Fe-4S] and a [4Fe-4S], and it also binds a zinc. An earlier structure of a related ferredoxin had its clusters converted artificially; here both clusters and the zinc site are intact, just as the organism makes them, at 2.0 Å resolution (paper).

It’s also one of the first proteins I crystallised. I grew the crystals at ITQB around 2000, between my undergraduate project and my PhD. They diffracted to 2.0 Å but were twinned, each with a different twinning ratio, so the structure took a long time to solve and refine. In the end the biochemistry caught up, it was important to get the structure out, and it was published in 2008.