Fang Jiahuiyu, Sarker Pranab, Qin Xiaoxue, Zhang Shuting, Zheng Size, Wei Tao
Department of Biomedical Engineering, University of South Carolina, Columbia, South Carolina, 29208, USA.
Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina, 29208, USA.
Nanoscale. 2025 Jul 16;17(28):16737-16747. doi: 10.1039/d5nr01891a.
Dissimilatory metal-reducing bacteria (DMRB) transfer electrons to extracellular metal oxides a multiheme cytochrome network. Coupling DMRB with iron oxide nanoparticles (NPs) enables continuous redox processes for various applications such as bioremediation and bioenergy. The conformation of the terminal decaheme cytochrome MtrF on the surface critically influences electron transfer (ET) efficiency. In this work, we used molecular dynamics simulations and master equations to study MtrF adsorption on 3.6 and 6.0 nm α-FeO NPs and its steady-state ET in water. Our study shows that the heme cofactors can have strong electrostatic interactions with iron oxide NP surfaces, promoting protein adsorption and interfacial ET, while a small number of hydration water molecules in the first hydration shell of the iron oxide NP form hydrogen bonds with protein residues, stabilizing them near the NP surface. The NP adsorption sites, which are favorable for the interfacial ET, are located at the heme groups near the terminals of two intersecting heme chains. Among these sites, the region around hemes 4 and 5, near the terminal of the long heme chain, along with heme 7 at the terminal of the staggered cross short chain, is found to be relatively energetically favorable and ET-efficient, anchoring MtrF in a lie-down orientation on the NP. As the NP size increases, more protein residues adsorb onto the NP, potentially hindering heme attachment. The MtrF adsorption on the NP distorts its heme network and affects ET, but has a negligible effect on the protein's secondary structure. The kinetic behavior of ET across MtrF and the rate-limiting step are governed by heme-NP contacts, the ratio of electron injection to ejection rate constants, and the direction of ET. Our study of protein-NP interactions is important for the development of bionanotechnologies.
异化金属还原菌（DMRB）将电子传递到细胞外金属氧化物——一个多血红素细胞色素网络。将DMRB与氧化铁纳米颗粒（NPs）耦合能够实现用于生物修复和生物能源等各种应用的连续氧化还原过程。末端十血红素细胞色素MtrF在表面的构象对电子转移（ET）效率有至关重要的影响。在这项工作中，我们使用分子动力学模拟和主方程来研究MtrF在3.6纳米和6.0纳米的α-FeO NPs上的吸附及其在水中的稳态ET。我们的研究表明，血红素辅因子可与氧化铁NP表面发生强烈的静电相互作用，促进蛋白质吸附和界面ET，而氧化铁NP第一水化层中的少量水分子与蛋白质残基形成氢键，将它们稳定在NP表面附近。有利于界面ET的NP吸附位点位于两条相交血红素链末端附近的血红素基团处。在这些位点中，长血红素链末端附近的血红素4和5周围区域，以及交错交叉短链末端的血红素7，在能量上相对有利且ET效率较高，使MtrF以平躺方向锚定在NP上。随着NP尺寸的增加，更多的蛋白质残基吸附到NP上，可能会阻碍血红素附着。MtrF在NP上的吸附会扭曲其血红素网络并影响ET，但对蛋白质的二级结构影响可忽略不计。跨MtrF的ET动力学行为和限速步骤受血红素-NP接触、电子注入与射出速率常数的比值以及ET方向的控制。我们对蛋白质-NP相互作用的研究对生物纳米技术的发展很重要。
