School of Biological and Chemical Sciences, Queen Mary University of London, London, UK.
Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, London, UK.
Nat Commun. 2021 Sep 10;12(1):5387. doi: 10.1038/s41467-021-25527-1.
Photosynthesis and respiration rely upon a proton gradient to produce ATP. In photosynthesis, the Respiratory Complex I homologue, Photosynthetic Complex I (PS-CI) is proposed to couple ferredoxin oxidation and plastoquinone reduction to proton pumping across thylakoid membranes. However, little is known about the PS-CI molecular mechanism and attempts to understand its function have previously been frustrated by its large size and high lability. Here, we overcome these challenges by pushing the limits in sample size and spectroscopic sensitivity, to determine arguably the most important property of any electron transport enzyme - the reduction potentials of its cofactors, in this case the iron-sulphur clusters of PS-CI (N0, N1 and N2), and unambiguously assign them to the structure using double electron-electron resonance. We have thus determined the bioenergetics of the electron transfer relay and provide insight into the mechanism of PS-CI, laying the foundations for understanding of how this important bioenergetic complex functions.
光合作用和呼吸作用依赖质子梯度来产生 ATP。在光合作用中，拟南芥光合复合物 I（PS-CI）被认为与铁氧还蛋白氧化和质体醌还原偶联，实现跨类囊体膜的质子泵浦。然而，人们对 PS-CI 的分子机制知之甚少，并且以前由于其体积大和高不稳定性，试图理解其功能的尝试都受到了挫折。在这里，我们通过推广大样本量和光谱灵敏度的极限来克服这些挑战，确定了任何电子传递酶最重要的性质 - 其辅助因子的还原电位，在这种情况下为 PS-CI 的铁硫簇（N0、N1 和 N2），并使用双电子-电子共振将其明确分配给结构。因此，我们确定了电子传递中继的生物能量学，并深入了解了 PS-CI 的机制，为理解这个重要的生物能量复合物的功能奠定了基础。
