Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Inorg Chem. 2013 Mar 18;52(6):2993-3000. doi: 10.1021/ic302404w. Epub 2013 Mar 4.
The first NMR structures of Cu(I) and Zn(II) peptide complexes as models of metallochaperones were derived with no predetermined binding mode. The cyclic peptide MDCSGCSRPG was reacted with Cu(I) and Zn(II) at low and moderate pH. This peptide features the conserved sequence of copper chaperones but with Asp at position 2 as appears in the zinc binding domain of ZntA. The structures were compared with those of the Cu(I) complexes of the wild-type sequence peptide MTCSGCSRPG. All analyses were conducted first with no metal-binding constraints to ensure accurate binding ligand assignment. Several structures included metal-Met binding, raising a possible role of Met in the metal transport mechanism. Both Cu(I) and Zn(II) gave different complexes when reacted with the peptide of the native-like sequence under different pH conditions, raising the possibility of pH-dependent transport mechanisms. Cu(I) bound the MTCSGCSRPG peptide through one Cys and the Met under acidic conditions and differently under basic conditions; Zn(II) bound the MDCSGCSRPG peptide through two Cys and the Met residues under acidic conditions and through one Cys and the Met under basic conditions, while Cu(I) bound the non-native Asp mutant peptide through the Asp and one Cys under both conditions, suggesting that Asp may inhibit pH-dependent binding for Cu(I). NOESY and ESI-HRMS supported the presence of an aqua ligand for Zn(II), which likely deprotonated under basic conditions to give a hydroxo group. Coordination similarities were detected among the model system and native proteins, which overall suggest that coordination flexibility is required for the function of metallochaperones.
作为金属伴侣蛋白模型的 Cu(I) 和 Zn(II) 肽复合物的第一个 NMR 结构是在没有预定结合模式的情况下推导出来的。该环状肽 MDCSGCSRPG 与 Cu(I) 和 Zn(II) 在低 pH 和中等 pH 下反应。该肽具有铜伴侣蛋白的保守序列，但在位置 2 处具有 Asp，这出现在 ZntA 的锌结合域中。将这些结构与野生型序列肽 MTCSGCSRPG 的 Cu(I) 复合物结构进行了比较。所有分析均首先在没有金属结合约束的情况下进行，以确保准确分配配体结合。当用天然样序列的肽在不同 pH 条件下反应时，有几个结构包括金属- Met 结合，这提出了 Met 在金属转运机制中的可能作用。当用天然样序列的肽在不同 pH 条件下反应时，Cu(I) 和 Zn(II) 分别给出了不同的配合物，这增加了 pH 依赖转运机制的可能性。Cu(I) 在酸性条件下通过一个 Cys 和 Met 结合 MTCSGCSRPG 肽，而在碱性条件下则不同；Zn(II) 在酸性条件下通过两个 Cys 和 Met 结合 MDCSGCSRPG 肽，而在碱性条件下通过一个 Cys 和 Met 结合，而 Cu(I) 在两种条件下均通过 Asp 和一个 Cys 结合非天然 Asp 突变肽，这表明 Asp 可能抑制 Cu(I) 的 pH 依赖结合。NOESY 和 ESI-HRMS 支持 Zn(II) 存在水配体，其在碱性条件下可能去质子化以给出一个羟基团。在模型系统和天然蛋白中检测到配位相似性，总体而言表明配位灵活性是金属伴侣蛋白功能所必需的。
