Rosell Federico I, Mauk Marcia R, Mauk A Grant
Department of Biochemistry and Molecular Biology and Centre for Blood Research, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
Biochemistry. 2007 Aug 14;46(32):9301-9. doi: 10.1021/bi7008079. Epub 2007 Jul 18.
Hemopexin (Hx) functions as a major heme scavenging protein in blood plasma and as such circulates without heme bound. In recent work, we have demonstrated that Hx binds metal ions in vitro in a manner that varies from one metal ion to another and that changes with heme binding. The structural consequences of metal ion binding to the form of Hx that dominates in plasma have now been evaluated by monitoring metal ion-linked changes in tertiary structure of the protein as reflected by changes in the near-UV CD spectrum and the ultraviolet absorption spectrum as a function of temperature. As part of this analysis we have developed thermally induced difference absorption maps (TIDAMs) to afford efficient visualization of temperature-dependent changes in the UV spectrum of Hx that are induced by binding of metal ions. The results are interpreted in terms of recent models proposed for metal ion binding sites on Hx and have implications for the possible modulation of heme binding to Hx by metal ions in vivo.
血红素结合蛋白（Hx）是血浆中主要的血红素清除蛋白，因此在循环时不结合血红素。在最近的研究中，我们已经证明，Hx在体外结合金属离子的方式因金属离子而异，并且会随着血红素的结合而变化。现在，通过监测蛋白质三级结构中与金属离子相关的变化（以近紫外圆二色光谱和紫外吸收光谱随温度的变化来反映），评估了金属离子与血浆中占主导地位的Hx形式结合的结构后果。作为该分析的一部分我们开发了热诱导差异吸收图谱（TIDAMs），以便有效地可视化由金属离子结合引起的Hx紫外光谱中与温度相关的变化。根据最近提出的关于Hx上金属离子结合位点的模型对结果进行了解释，这些结果对体内金属离子可能调节血红素与Hx的结合具有启示意义。
