Lyu Hui, Lazár Dušan
School of Biological Science and Agriculture, Qiannan Normal University for Nationalities, Duyun, China.
Department of Biophysics, Faculty of Science, Palacký University, Olomouc, Czechia.
Front Plant Sci. 2022 Jul 28;13:945675. doi: 10.3389/fpls.2022.945675. eCollection 2022.
The transthylakoid membrane potential (ΔΨ) is essential because it can drive the ATP synthesis through the CF-CF type of ATP-synthase in chloroplasts as an energetic equivalent similar to ΔpH. In addition, a high fraction of proton motive force (PMF) stored as the ΔΨ component is physiologically important in the acclimation of photosynthesis to environmental stresses. It has been shown that ΔΨ is the sum of the Donnan potential difference (ΔΨ) and the diffusion potential difference (ΔΨ). Specifically, ΔΨ, ΔΨ, and ΔΨ are strongly associated with the ionic activities near the membrane surface, particularly, the extent of ion binding to the charged/neutral sites adjacent to the membrane surface. However, an in-depth analysis of the effect of altered cationic binding to the membrane surface on adjusting the transthylakoid electric potentials (ΔΨ, ΔΨ, and ΔΨ) is still missing. This lack of a mechanistic understanding is due to the experimental difficulty of closely observing cations binding to the membrane surface . In this work, a computer model was proposed to investigate the transthylakoid electric phenomena in the chloroplast focusing on the interaction between cations and the negative charges close to the membrane surface. By employing the model, we simulated the membrane potential and consequently, the measured ECS traces, proxing the ΔΨ, were well described by the computing results on continuous illumination followed by a dark-adapted period. Moreover, the computing data clarified the components of transthylakoid membrane potential, unraveled the functional consequences of altered cationic attachment to the membrane surface on adjusting the transthylakoid electric potential, and further revealed the key role played by Donnan potential in regulating the energization of the thylakoid membrane. The current model for calculating electric potentials can function as a preliminary network for the further development into a more detailed theoretical model by which multiple important variables involved in photosynthesis can be explored.
类囊体膜电位（ΔΨ）至关重要，因为它能像ΔpH一样，作为一种能量等价物，通过叶绿体中的CF - CF型ATP合酶驱动ATP合成。此外，以ΔΨ成分形式储存的大部分质子动力（PMF）在光合作用适应环境胁迫方面具有重要生理意义。研究表明，ΔΨ是唐南电位差（ΔΨ）和扩散电位差（ΔΨ）之和。具体而言，ΔΨ、ΔΨ和ΔΨ与膜表面附近的离子活性密切相关，特别是离子与膜表面相邻的带电/中性位点的结合程度。然而，目前仍缺乏对膜表面阳离子结合变化对类囊体跨膜电位（ΔΨ、ΔΨ和ΔΨ）调节作用的深入分析。这种对机制理解的缺乏是由于难以直接观察阳离子与膜表面的结合。在这项工作中，我们提出了一个计算机模型来研究叶绿体中的类囊体电现象，重点关注阳离子与膜表面附近负电荷之间的相互作用。通过使用该模型，我们模拟了膜电位，因此，在持续光照后紧接着暗适应期的情况下，测量得到的代表ΔΨ的胞外空间（ECS）轨迹能够被计算结果很好地描述。此外，计算数据阐明了类囊体膜电位的组成部分，揭示了膜表面阳离子附着变化对调节类囊体跨膜电位的功能影响，并进一步揭示了唐南电位在调节类囊体膜能量化过程中所起的关键作用。当前用于计算电位的模型可作为一个初步网络，用于进一步发展成更详细的理论模型，借此可以探索光合作用中涉及的多个重要变量。
