Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav), Mexico City, Mexico.
Dalton Trans. 2018 Jul 17;47(28):9274-9282. doi: 10.1039/c7dt03400h.
The cellular prion protein (PrPC) is a copper binding protein that undergoes post-translational modifications, such as endoproteolytic alpha cleavage, which occurs in the vicinity of the His111 Cu binding site. Alpha cleavage processing of PrPC is considered to be neuroprotective since the cleavage site is located in a region that is key to the conversion of PrPC into the infectious scrapie isoform (PrPSc), yielding a membrane bound C1 fragment of PrPC that still contains His111. In this work, we use hPrP(111-115) fragment as a model peptide to evaluate the impact of alpha cleavage processing of PrPC in its ability to coordinate Cu(ii) ions at His111. By using different spectroscopic techniques such as electronic absorption, circular dichroism, nuclear magnetic resonance, and electron paramagnetic resonance, this study demonstrates that Cu(ii) binding to the cleaved His111 site is highly dependent on Cu and proton concentrations. The imidazole group of His111 and its free NH2 terminus emerge as the main anchoring sites for Cu(ii) coordination, yielding very different complexes from those characterized for the intact His111 site in the full protein. Different Cu(ii) coordination modes that could form with the alpha cleaved PrPC under physiological conditions are identified and characterized. Overall, this study contributes to understand how alpha cleavage processing of PrPC impacts its Cu(ii) binding properties at His111. While the functional implications of Cu binding to the cleaved PrPC remain to be discovered, proteolytic processing of PrPC and its Cu binding features appear to be molecular events that might be strongly linked to its cellular function.
细胞朊病毒蛋白 (PrPC) 是一种铜结合蛋白，可发生翻译后修饰，如靠近 His111 铜结合位点的内切 α 裂解。PrPC 的 α 裂解加工被认为具有神经保护作用，因为裂解位点位于关键区域，该区域将 PrPC 转化为传染性瘙痒病异构体 (PrPSc)，产生仍然含有 His111 的 PrPC 的膜结合 C1 片段。在这项工作中，我们使用 hPrP(111-115) 片段作为模型肽来评估 PrPC 的 α 裂解加工对其在 His111 处协调 Cu(ii) 离子能力的影响。通过使用不同的光谱技术，如电子吸收、圆二色性、核磁共振和电子顺磁共振，本研究表明，Cu(ii)与裂解 His111 位点的结合高度依赖于 Cu 和质子浓度。His111 的咪唑基团及其游离的 NH2 末端成为 Cu(ii)配位的主要锚定点，产生与完整蛋白中完整 His111 位点所表征的非常不同的配合物。鉴定并表征了在生理条件下可能与 α 裂解 PrPC 形成的不同 Cu(ii)配位模式。总的来说，这项研究有助于了解 PrPC 的 α 裂解加工如何影响其在 His111 处的 Cu(ii)结合特性。虽然 Cu 与裂解 PrPC 的结合的功能意义仍有待发现，但 PrPC 的蛋白水解加工及其 Cu 结合特征似乎是与细胞功能密切相关的分子事件。
