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C-terminal Cysteines of CueR Act as Auxiliary Metal Site Ligands upon HgII Binding-A Mechanism To Prevent Transcriptional Activation by Divalent Metal Ions?

ABSTRACT: Intracellular CuI is controlled by the transcriptional regulator CueR, which effectively discriminates between monovalent and divalent metal ions. It is intriguing that HgII does not activate transcription, as bis-thiolate metal sites exhibit high affinity for HgII . Here the binding of HgII to CueR and a truncated variant, ?C7-CueR, without the last 7 amino acids at the C-terminus including a conserved CCHH motif is explored. ESI-MS demonstrates that up to two HgII bind to CueR, while ?C7-CueR accommodates only one HgII . 199m Hg PAC and UV absorption spectroscopy indicate HgS2 structure at both the functional and the CCHH metal site. However, at sub-equimolar concentrations of HgII at pH?8.0, the metal binding site displays an equilibrium between HgS2 and HgS3 , involving cysteines from both sites. We hypothesize that the C-terminal CCHH motif provides auxiliary ligands that coordinate to HgII and thereby prevents activation of transcription.

SUBMITTER: Balogh RK

PROVIDER: S-EPMC6899792 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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C-terminal Cysteines of CueR Act as Auxiliary Metal Site Ligands upon HgII Binding-A Mechanism To Prevent Transcriptional Activation by Divalent Metal Ions?

Balogh Ria K RK Gyurcsik Béla B Hunyadi-Gulyás Éva É Schell Juliana J Thulstrup Peter W PW Hemmingsen Lars L Jancsó Attila A

Chemistry (Weinheim an der Bergstrasse, Germany) 20191015 66

Intracellular CuI is controlled by the transcriptional regulator CueR, which effectively discriminates between monovalent and divalent metal ions. It is intriguing that HgII does not activate transcription, as bis-thiolate metal sites exhibit high affinity for HgII . Here the binding of HgII to CueR and a truncated variant, ΔC7-CueR, without the last 7 amino acids at the C-terminus including a conserved CCHH motif is explored. ESI-MS demonstrates that ...[more]

PMID: 31365771

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Project description:Divalent cations, especially Ca2+ and Mg2+, play a vital role in the function of biomolecules and making them important to be constituents in samples for in vitro biophysical and biochemical characterizations. Although lipid nanodiscs are becoming valuable tools for structural biology studies on membrane proteins and for drug delivery, most types of nanodiscs used in these studies are unstable in the presence of divalent metal ions. To avoid the interaction of divalent metal ions with the belt of the nanodiscs, synthetic polymers have been designed and demonstrated to form stable lipid nanodiscs under such unstable conditions. Such polymer-based nanodiscs have been shown to provide an ideal platform for structural studies using both solid-state and solution NMR spectroscopies because of the near-native cell-membrane environment they provide and the unique magnetic-alignment behavior of large-size nanodiscs. In this study, we report an investigation probing the effects of Ca2+ and Mg2+ ions on the formation of polymer-based lipid nanodiscs and the magnetic-alignment properties using a synthetic polymer, styrene maleimide quaternary ammonium (SMA-QA), and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipids. Phosphorus-31 NMR experiments were used to evaluate the stability of the magnetic-alignment behavior of the nanodiscs for varying concentrations of Ca2+ or Mg2+ at different temperatures. It is remarkable that the interaction of divalent cations with lipid headgroups promotes the stacking up of nanodiscs that results in the enhanced magnetic alignment of nanodiscs. Interestingly, the reported results show that both the temperature and the concentration of divalent metal ions can be optimized to achieve the optimal alignment of nanodiscs in the presence of an applied magnetic field. We expect the reported results to be useful in the design of nanodisc-based nanoparticles for various applications in addition to atomic-resolution structural and dynamics studies using NMR and other biophysical techniques.

Dataset Information

C-terminal Cysteines of CueR Act as Auxiliary Metal Site Ligands upon HgII Binding-A Mechanism To Prevent Transcriptional Activation by Divalent Metal Ions?

Publications

C-terminal Cysteines of CueR Act as Auxiliary Metal Site Ligands upon Hg<sup>II</sup> Binding-A Mechanism To Prevent Transcriptional Activation by Divalent Metal Ions?

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