COLLABORATIVE RESEARCH: Redox metallo-proteins and conformational gating in electron transfer to ferric minerals

怀俄明大学和爱达荷州立大学的这项合作项目将研究金属还原微生物细胞膜上的电子从矿物氧化物表面转移到c型细胞色素的过程。还将研究氧化物与铁硫蛋白和其他生物分子的相互作用。研究中的主要假设是看氧化物表面是否会触发矿物表面蛋白质的构象变化，从而导致有利于电子转移的蛋白质的氧化还原电势发生变化。这项研究的动机是因为金属还原微生物及其如何与环境相互作用引起了人们的极大兴趣，不仅因为它们参与了铁和其他金属的全球氧化还原循环，还因为它们能够在化学上固定环境中的各种有毒金属，包括放射性核素。研究将使用商业上可用的蛋白质，以及实验室中从金属还原细菌中提纯的蛋白质。将进行吸附研究，以了解发生最佳蛋白质-矿物相互作用的水条件。这项研究将考察外膜蛋白对赤铁矿和针铁矿的吸附随pH、离子强度、时间、温度和磷酸盐组成的变化。在不同的地球化学条件下，蛋白质在吸附状态下的氧化还原状态也将被检测。将进行表面成像技术和表征，如原子力和扫描隧道电子显微镜，以及XANES，EXAFS和UV-Vis光谱。二次谐波产生将被用来检测吸附在氧化物表面的选定分子的取向。研究中蛋白质氧化还原性质的变化将与构象变化相关联，并将确定吸附分子的极化率和吸附状态下分子的尺寸。这项研究的更广泛影响包括开发蛋白质功能化电极的科学基础，使我们能够在传感器应用中利用蛋白质的特定功能，有毒金属的生物修复策略，以及提高我们对金属生物修复的理解。

This collaborative project between researchers at the University of Wyoming and Idaho State University will examine the transfer of electrons from mineral oxide surfaces to c-type cytochromes from the cell membranes of metal-reducing microbes. Oxide interactions with iron-sulfur proteins and other biomolecules will also be investigated. The main hypothesis under investigation is to see if oxide surfaces "trigger" conformation changes in proteins on mineral surfaces that can result in a shift in the redox potential of the protein that favors electron transfer. This study was motivated because metal reducing microorganisms and how they interact with their environment are of great interest not only because they are involved in the global redox cycling of iron and other metals, but also because they are able to chemically immobilize a variety of toxic metals in the environment, including radionuclides. Research will be carried out with commercially available proteins, as well as proteins purified from metal-reducing bacteria in the laboratory. Sorption studies to understand the aqueous conditions under which optimal protein-mineral interaction happen will be conducted. The research will examine outer membrane protein adsorption to hematite and goethite as a function of pH, ionic strength, time, temperature and phosphate composition. The redox state of proteins in the adsorbed state under different geochemical conditions will also be examined. Surface imaging techniques and characterizations such as atomic force and scanning tunneling electron microscopy will be carried out as will XANES, EXAFS, and UV-VIS spectroscopy. Second harmonic generation will be used to examine the orientation of selected molecules adsorbed to oxide surfaces. Changes in the redox properties of the proteins under investigation will be correlated with conformational changes, and the polarizability of the adsorbed molecules and dimensions of the molecules in the adsorbed state will be determined. Broader impacts of this study include the scientific basis for development of protein-functionalized electrodes that will allow us to utilize the specific function of proteins in sensor applications, bioremediation strategies for toxic metals, and improving our understanding of bioremediation of metals.