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

• Published in: Biochimica et biophysica acta. General subjects Vol. 1865; no. 3; p. 129810
• Main Authors: Taher, Raleb, de Rosny, Eve
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.03.2021; Elsevier
• Subjects: Amino Acid Sequence; Arabinose - chemistry; Arabinose - metabolism; atomic absorption spectrometry; Binding Sites; Biochemistry, Molecular Biology; circular dichroism spectroscopy; Cloning, Molecular; crosslinking; Crystallography, X-Ray; cysteine; Envelope stress response; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; fluorescence; Gene Expression Regulation, Bacterial; Genetic Vectors - chemistry; Genetic Vectors - metabolism; histidine kinase; homeostasis; Life Sciences; Models, Molecular; Periplasm - genetics; Periplasm - metabolism; Protein Binding; Protein Conformation, alpha-Helical; Protein Conformation, beta-Strand; Protein Interaction Domains and Motifs; Protein Multimerization; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; small-angle X-ray scattering; stress response; Structural Biology; Structure-Activity Relationship; toxicity; Trans-Activators - chemistry; Trans-Activators - genetics; Trans-Activators - metabolism; Two-component systems; X-radiation; zinc; Zinc - chemistry; Zinc - metabolism; Zinc binding proteins; Zra system; ZraP; ZraS; ZraS; Zinc binding proteins; Two-component systems; ZraP; Envelope stress response; Zra system
• DOI: 10.1016/j.bbagen.2020.129810
• ISSN: 0304-4165; 1872-8006

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 to its histidine kinase sensor protein (ZraS) and its response regulator (ZraR) components. Furthermore, although it is activated by Zn2+, it is not involved in zinc homeostasis or protection against zinc toxicity. Here, we mainly focus on ZraS but also provide information on ZraP. The purified periplasmic domain of ZraS and ZraP were characterized using biophysical and 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 and small-angle X-ray scattering (SAXS). In-vivo experiments were carried out to determine the redox state of the cysteine residue in ZraP and the consequences for the cell of an over-activation of the Zra system. We show that ZraS binds one Zn2+ molecule with high affinity resulting in conformational changes of the periplasmic domain, consistent with a triggering function of the metal ion. We also demonstrate that, in the periplasm, the only cysteine residue of ZraP is at least partially reduced. Using SAXS, we conclude that the previously determined X-ray structure is different from the structure in solution. Our results allow us to propose a general mechanism for the Zra system activation and to compare it to the homologous Cpx system. We bring new input on the so far poorly described Zra system and notably on ZraS. •ZraS contains one high affinity zinc binding site.•Zinc binding to ZraS periplasmic domain induces conformational changes.•ZraP only cysteine is reduced in vivo.•In solution and at high concentration ZraP is a globular octamer.•Over-activation of the Zra system reduces cell division rate.