“…In addition to Cys residues, iron is frequently used by regulatory proteins to sense O 2 , NO·, carbon monoxide (CO), O 2 · â , or redox cycling compounds. Iron can be found as (i) mononuclear centers in Fur, PerR (peroxide regulator) or NorR (nitric oxide regulator), (ii) [2Fe-2S] and [4Fe-4S] clusters in SoxR (superoxide regulator), FNR (fumarate-nitrate reduction regulator) or NsrR (nitric oxide-responsive regulator), or (iii) heme prosthetic groups in dormancy survival regulatory proteins DosT and DosS, or DNR (dissimilative nitrate respiration regulator) (Crack et al, 2014; Ji et al, 2015; Lobato et al, 2014; Ma et al, 2012). Molecular mechanisms of redox sensing rely on protein conformational changes triggered by interaction with reactive oxygen and nitrogen species (see accompanying review in this issue, Fang et al, 2016) (Figure 2B).…”