Single-molecule study of redox control involved in establishing the spinach plastocyanin-cytochrome bf electron transfer complex
Single-molecule study of redox control involved in establishing the spinach plastocyanin-cytochrome bf electron transfer complex
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建立菠菜质体蓝素-细胞色素 bf 电子转移复合物的氧化还原控制的单分子研究
DOI：
10.1016/j.bbabio.2019.06.013
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Mayneord G
中科院分区：
文献类型：
--
作者：
Mayneord G
小分子可扩散的氧化还原蛋白在生物能量系统中起着普遍的作用，促进了膜结合复合体之间的电子转移。维持较高的ET周转率要求外源性伙伴和膜结合伙伴之间的联系具有高度的特异性，但也足够弱，以促进ET后的快速分离。在氧合光合作用中，小分子可溶性电子载体蛋白胞质蓝蛋白(Pc)在膜整体细胞色素b6f(Cytb6f)和光系统I(PSI)复合体之间传递电子。在这里，我们使用峰力定量纳米机械映射(PF-QNM)原子力显微镜(AFM)来量化同源ET伙伴之间的瞬时相互作用所涉及的动态力。带有Pc分子官能化的AFM探针与固定在平面硅表面的Cytb6f络合物接触。PF-QNM以皮牛力分辨率在单分子水平上询问Cytb6f-Pc相互作用的解结力，并在与体内ET时间相当的时间尺度上(约120 μS)。使用这种方法，我们表明，虽然解结力保持不变，但当Pc和Cytb6处于相反的氧化还原态时，相互作用频率增加五倍以上，因此Cytb6f和Pc共因子上的互补电荷可能有助于启动ET络合物形成的静电力。这些结果表明，对接界面的形成受氧化还原态控制，这降低了Pc和Cytb6f分子在相同氧化还原状态下发生无效相遇的几率，确保了这种中心反应在光合作用ET的Z-方案中的有效性和方向性。
Small diffusible redox proteins play a ubiquitous role in bioenergetic systems, facilitating electron transfer (ET) between membrane bound complexes. Sustaining high ET turnover rates requires that the association between extrinsic and membrane-bound partners is highly specific, yet also sufficiently weak to promote rapid post-ET separation. In oxygenic photosynthesis the small soluble electron carrier protein plastocyanin (Pc) shuttles electrons between the membrane integral cytochromeb6f(cytb6f) and photosystem I (PSI) complexes. Here we use peak-force quantitative nanomechanical mapping (PF-QNM) atomic force microscopy (AFM) to quantify the dynamic forces involved in transient interactions between cognate ET partners. An AFM probe functionalised with Pc molecules is brought into contact with cytb6fcomplexes, immobilised on a planar silicon surface. PF-QNM interrogates the unbinding force of the cytb6f-Pcinteractions at the single molecule level with picoNewton force resolution and on a time scale comparable to the ET time in vivo (ca. 120 μs). Using this approach, we show that although the unbinding force remains unchanged the interaction frequency increases over five-fold when Pc and cytb6fare in opposite redox states, so complementary charges on the cytb6fand Pc cofactors likely contribute to the electrostatic forces that initiate formation of the ET complex. These results suggest that formation of the docking interface is under redox state control, which lowers the probability of unproductive encounters between Pc and cytb6fmolecules in the same redox state, ensuring the efficiency and directionality of this central reaction in the ‘Z-scheme’ of photosynthetic ET.