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

TY - JOUR

T1 - C-terminal Cysteines of CueR Act as Auxiliary Metal Site Ligands upon HgII Binding—A Mechanism To Prevent Transcriptional Activation by Divalent Metal Ions?

AU - Balogh, Ria K.

AU - Gyurcsik, Béla

AU - Hunyadi-Gulyás, Éva

AU - Schell, Juliana

AU - Thulstrup, Peter W.

AU - Jancsó, Attila

AU - Hemmingsen, Lars Bo Stegeager

PY - 2019/11/27

Y1 - 2019/11/27

N2 - 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 up to two HgII bind to CueR, while ΔC7-CueR accommodates only one HgII. 199mHg 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.

AB - 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 up to two HgII bind to CueR, while ΔC7-CueR accommodates only one HgII. 199mHg 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.

KW - coordination modes

KW - CueR metalloregulatory protein

KW - mercury

KW - metal ion selectivity

KW - perturbed angular correlation (PAC) spectroscopy

U2 - 10.1002/chem.201902940

DO - 10.1002/chem.201902940

M3 - Letter

C2 - 31365771

AN - SCOPUS:85074420724

SN - 0947-6539

VL - 25

SP - 15030

EP - 15035

JO - Chemistry: A European Journal

JF - Chemistry: A European Journal

IS - 66

ER -