C-terminal Cysteines of CueR Act as Auxiliary Metal Site Ligands upon HgII Binding-A Mechanism To Prevent Transcriptional Activation by Divalent Metal Ions?
C-terminal Cysteines of CueR Act as Auxiliary Metal Site Ligands upon HgII Binding-A Mechanism To Prevent Transcriptional Activation by Divalent Metal Ions?
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DOI：
10.1002/chem.201902940
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发表时间：
2019-10-15
影响因子：
4.3
通讯作者：
Jancso, Attila
中科院分区：
文献类型：
--
作者：
Balogh, Ria K.;Gyurcsik, Bela;Jancso, Attila
细胞内 Cu-I 受转录调节因子 CueR 控制，可有效区分单价和二价金属离子。有趣的是，Hg-II 不会激活转录，因为双硫醇盐金属位点对 Hg-II 表现出高亲和力。这里探讨了 Hg-II 与 CueR 和截短变体 Delta C7-CueR 的结合，该变体在 C 末端没有最后 7 个氨基酸，包括保守的 CCHH 基序。 ESI-MS 表明最多有两个 Hg-II 与 CueR 结合，而 Delta C7-CueR 仅容纳一个 Hg-II。 Hg-199m PAC 和紫外吸收光谱表明功能位点和 CCHH 金属位点均具有 HgS2 结构。然而，在 pH 8.0 的亚等摩尔浓度的 Hg-II 下，金属结合位点显示出 HgS2 和 HgS3 之间的平衡，涉及两个位点的半胱氨酸。我们假设 C 端 CCHH 基序提供了与 Hg-II 协调的辅助配体，从而阻止转录激活。
Intracellular Cu-I is controlled by the transcriptional regulator CueR, which effectively discriminates between monovalent and divalent metal ions. It is intriguing that Hg-II does not activate transcription, as bis-thiolate metal sites exhibit high affinity for Hg-II. Here the binding of Hg-II to CueR and a truncated variant, Delta 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 Hg-II bind to CueR, while Delta C7-CueR accommodates only one Hg-II. Hg-199m PAC and UV absorption spectroscopy indicate HgS2 structure at both the functional and the CCHH metal site. However, at sub-equimolar concentrations of Hg-II 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 Hg-II and thereby prevents activation of transcription.