Department of Chemistry, University of California, Berkeley, California 94720, United States.
Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States.
ACS Nano. 2021 May 25;15(5):8110-8119. doi: 10.1021/acsnano.0c07165. Epub 2020 Dec 7.
Bioenergetic processes in nature have relied on networks of cofactors for harvesting, storing, and transforming the energy from sunlight into chemical bonds. Models mimicking the structural arrangement and functional crosstalk of the cofactor arrays are important tools to understand the basic science of natural systems and to provide guidance for non-natural functional biomaterials. Here, we report an artificial multiheme system based on a circular permutant of the tobacco mosaic virus coat protein (cpTMV). The double disk assembly of cpTMV presents a gap region sandwiched by the two -symmetrically related disks. Non-native bis-his coordination sites formed by the mutation of the residues in this gap region were computationally screened and experimentally tested. A cpTMV mutant Q101H was identified to create a circular assembly of 17 protein-embedded hemes. Biophysical characterization using X-ray crystallography, cyclic voltammetry, and electron paramagnetic resonance (EPR) suggested both structural and functional similarity to natural multiheme cytochrome proteins. This protein framework offers many further engineering opportunities for tuning the redox properties of the cofactors and incorporating non-native components bearing varied porphyrin structures and metal centers. Emulating the electron transfer pathways in nature using a tunable artificial system can contribute to the development of photocatalytic materials and bioelectronics.
自然界中的生物能量过程依赖于辅助因子网络来收集、储存和转化来自阳光的能量，形成化学键。模拟辅助因子阵列的结构排列和功能串扰的模型是理解自然系统基础科学的重要工具，并为非自然功能生物材料提供指导。在这里，我们报告了一种基于烟草花叶病毒衣壳蛋白（cpTMV）环化变构体的人工多血红素系统。cpTMV 的双圆盘组装呈现出由两个对称相关圆盘夹在中间的间隙区域。通过突变该间隙区域中的残基，计算筛选和实验测试了非天然双组氨酸配位位点。鉴定出 cpTMV 突变体 Q101H 以创建 17 个蛋白嵌入血红素的环形组装。使用 X 射线晶体学、循环伏安法和电子顺磁共振（EPR）进行的生物物理特性分析表明，它与天然多血红素细胞色素蛋白在结构和功能上具有相似性。该蛋白框架为调节辅助因子的氧化还原性质以及结合具有不同卟啉结构和金属中心的非天然组件提供了许多进一步的工程机会。使用可调人工系统模拟自然界中的电子转移途径，可以为光催化材料和生物电子学的发展做出贡献。
