Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, 3200003 Haifa, Israel.
Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, 3200003 Haifa, Israel
Proc Natl Acad Sci U S A. 2020 Dec 22;117(51):32260-32266. doi: 10.1073/pnas.2008741117. Epub 2020 Dec 7.
The fundamental biological process of electron transfer (ET) takes place across proteins with common ET pathways of several nanometers. Recent discoveries push this limit and show long-range extracellular ET over several micrometers. Here, we aim in deciphering how protein-bound intramolecular cofactors can facilitate such long-range ET. In contrast to natural systems, our protein-based platform enables us to modulate important factors associated with ET in a facile manner, such as the type of the cofactor and its quantity within the protein. We choose here the biologically relevant protoporphyrin molecule as the electron mediator. Unlike natural systems having only Fe-containing protoporphyrins, i.e., heme, as electron mediators, we use here porphyrins with different metal centers, or lacking a metal center. We show that the metal redox center has no role in ET and that ET is mediated solely by the conjugated backbone of the molecule. We further discuss several ET mechanisms, accounting to our observations with possible contribution of coherent processes. Our findings contribute to our understanding of the participation of heme molecules in long-range biological ET.
电子转移（ET）的基本生物过程发生在具有数纳米常见 ET 途径的蛋白质之间。最近的发现突破了这一限制，显示出长达数微米的细胞外远距离 ET。在这里，我们旨在破译蛋白质结合的分子内辅因子如何促进这种长距离 ET。与天然系统相比，我们的基于蛋白质的平台使我们能够以简单的方式调节与 ET 相关的重要因素，例如辅因子的类型及其在蛋白质中的数量。我们在这里选择生物相关的原卟啉分子作为电子介体。与仅含有 Fe 的原卟啉（即血红素）作为电子介体的天然系统不同，我们使用具有不同金属中心或没有金属中心的卟啉。我们表明，金属氧化还原中心在 ET 中没有作用，ET 仅由分子的共轭主链介导。我们进一步讨论了几种 ET 机制，根据我们的观察结果，可能涉及相干过程的贡献。我们的发现有助于我们理解血红素分子在长距离生物 ET 中的参与。
