How much one electron can do

Although living organisms are mainly composed of organic matter, many very essential natural processes depend directly on inorganic factors. The function of nearly 40% of all proteins function depends on one or more metal ions. Among the biological metal-containing cofactors, the iron-sulfur [Fe-S] clusters, ubiquitous in animals, plants and bacteria, play fundamental roles in electron transfer (respiration, photosynthesis) and the regulation of gene expression through DNA binding.
At the IBS, the Metalloproteins Unit is interested, among many others metal-containing proteins, in the bacterial metalloprotein regulator RsrR. RsrR, which coordinates a [2Fe-2S] cluter, controls the expression of certain genes involved in the redox processes of the cell. Previous studies have shown that RsrR has the particularity of modulating its binding to DNA through the reduction of its [2Fe-2S] cluster by one electron. The RsrR crystal structure shows that the cluster has a coordination previously never observed in a protein consisting of residues from two cysteines, a glutamate and a histidine. The RsrR crystals also show that the rotation of a tryptophan side chain could modulate its attachment to DNA.
This work provides the structural basis to understand how an effector as small as an electron can induce the protein-based structural changes needed for the adaptation of a bacterium to its environment.

The Crystal Structure of the Transcription Regulator RsrR Reveals a [2Fe-2S] Cluster Coordinated by Cys, Glu and His Residues. Volbeda A, Pellicer Martinez MT, Crack JC, Amara P, Gigarel O, Munnoch JT, Hutchings MI, Darnault C, Le Brun NE, Fontecilla-Camps JC. J Am Chem Soc. 2019 Jan 18. doi: 10.1021/jacs.8b10823.