A structure-function study of ZraP and ZraS provides new insights into the two-component system Zra

Zra belongs to the envelope stress response (ESR) two-component systems (TCS). It is atypical because of its third periplasmic repressor partner (ZraP), in addition histidine kinase sensor protein (ZraS) and regulator (ZraR) components. Furthermore, although it activated by Zn2+, not involved zinc homeostasis or protection against toxicity. Here, we mainly focus on ZraS but also provide information ZraP. The purified domain ZraP were characterized using biophysical biochemical technics: multi-angle laser light scattering (MALLS), circular dichroism (CD), differential scanning fluorescence (DSF), inductively coupled plasma atomic emission spectroscopy (ICP-AES), cross-linking small-angle X-ray (SAXS). In-vivo experiments carried out determine redox state cysteine residue consequences for cell an over-activation system. We show that binds one Zn2+ molecule with high affinity resulting conformational changes domain, consistent a triggering function metal ion. demonstrate that, periplasm, only at least partially reduced. Using SAXS, conclude previously determined structure different from solution. Our results allow us propose general mechanism system activation compare homologous Cpx bring new input so far poorly described notably ZraS.