The supramolecular arrangement of respiratory complexes into supercomplexes is widely accepted. The common feature observed in the supercomplex architecture from organisms of diverse phylogenetic origin is the reduction of the distance between cytochrome bc₁ (complex III) and cytochrome c oxidase (complex IV). Such an arrangement reduces the dimensionality (from 3D to 2D) of the diffusional search of cytochrome c as the electron carrier that connects both complexes. In this scenario, our recent finding of additional binding sites for cytochrome c reinforces the concept of a “restrained 2D sliding pathway” onto the supercomplex surface. Herein, we analyze novel mechanistic insights into electron transfer towards cytochrome c, including modulation of the redox potential by physical contact as well as gated, long-range electron transfer through an aqueous solution. These data establish a new horizon for the understanding of electron transfer mechanisms beyond unique and well-orientated protein complexes. Multiple and dynamic long-distance conformational ensembles compatible with electron transfer could indeed contribute to the rapid adjustment of electron flow in response to changing cellular conditions.

呼吸复合物超分子排列成超复合物被广泛接受。在来自不同系统发育起源的生物体的超复合体结构中观察到的共同特征是细胞色素bc ₁（复合体 III）和细胞色素c氧化酶（复合体 IV）之间的距离减小。这种布置降低了细胞色素c作为连接两个复合物的电子载体的扩散搜索的维度（从 3D 到 2D）。在这种情况下，我们最近发现了细胞色素c的其他结合位点强化了超复杂表面上“受约束的 2D 滑动路径”的概念。在这里，我们分析了电子向细胞色素c转移的新机制见解，包括通过物理接触调节氧化还原电位以及通过水溶液进行门控远程电子转移。这些数据为理解独特且定向良好的蛋白质复合物之外的电子转移机制开辟了新的视野。与电子转移兼容的多重动态长距离构象集合确实有助于快速调整电子流以响应不断变化的细胞条件。