Membrane and Cell BiologyMembrane and Cell BiologyБиологические мембраны0233-47553034-5219The Russian Academy of Sciences40597410.7868/S3034521926010012ArticlesСТАТЬИResearch ArticleTransmembrane Proton Transfer in Chloroplasts in Silico: pH Homeostasis of Lumen, Stroma, and CytosolТрансмембранный перенос протонов в хлоропластах in silico: pH-гомеостаз люмена, стромы и цитозоляVershubskiiA. VВершубскийА. В-TikhonovA. NТихоновА. Нan_tikhonov@mail.ruLomonosov Moscow State UniversityМосковский государственный университет имени М.В. Ломоносова15022026431VOL 43, NO1 ()ТОМ 43, №1 ()31703042026Copyright ©; 2026, Russian Academy of SciencesCopyright ©; 2026, Российская академия наук2026Russian Academy of SciencesРоссийская академия наукhttps://journals.rcsi.science/0233-4755/article/view/405974

The research described in this paper is based on a mathematical model of the light stages of photosynthesis, which considers the processes of electron and proton transport in chloroplasts. It examines the redox transformations of the photoreaction centers PS I (P700), PS II (P680) and other electron transport chain carriers–ferredoxin (Fd), plastoquinone (PQ) and plastocyanin (Pc)–as well as the transmembrane proton transport associated with electron transport and ATP synthesis by membrane ATP synthase. The simulation results are in good agreement with the literature data on pH measurements in the lumen (pHin) and stroma (pHout) of chloroplasts at different cytosol pH values (pHcyt). The steady-state pH values established in these compartments when chloroplasts are illuminated under photophosphorylation conditions satisfy the following inequalities: pHin ≈ 6.2–6.4 < pHcyt ≈ 7.2–7.4 < pHout ≈ 7.8–8.0. Variation of the pHcyt model parameter affects the electron flows carried by different electron transport pathways, such as non-cyclic electron transport from PS II to PS I and further into the Calvin–Benson cycle, cyclic electron transport around PS I, and pseudocyclic electron transport involving molecular oxygen (the “water – water” cycle). It has also been shown that sufficiently strong acidification of the cytosol (pHcyt < 7) reduces electron efflux from the acceptor side of PS I (non-cyclic and pseudocyclic electron transport) and stimulates cyclic electron transport around PS I, and also decreases the rate of pH-dependent ATP synthesis.

В основе исследования, описываемого в настоящей работе, – математическая модель световых стадий фотосинтеза, в которой рассматриваются процессы электронного и протонного транспорта в хлоропластах. Моделируются редокс-превращения фотореакционных центров ФС I (P700), ФС II (P680) и других переносчиков цепи электронного транспорта – ферредоксин (Fd), пластохинон (PQ) и пластоцианин (Pc), а также сопряженный с электронным транспортом трансмембранный перенос протонов и синтез ATP за счет работы мембранной ATP-синтазы. Результаты моделирования хорошо согласуются с литературными данными по измерениям pH в люмене (pHin) и в строме (pHout) хлоропластов при разных значениях pH цитозоля (pHcyt). Стационарные значения pH, устанавливающиеся в этих компартментах при освещении хлоропластов в условиях фотофосфорилирования, удовлетворяют неравенствам: pHin ≈ 6.2–6.4 < pHcyt ≈ 7.2–7.4 < pHout ≈ 7.8–8.0. Варьирование параметра модели pHcyt влияет на потоки электронов, переносимых по разным путям электронного транспорта, таким как нециклический транспорт электронов от ФС II к ФС I и далее в цикл Кальвина – Бенсона, циклический перенос электронов вокруг ФС I и псевдоциклический перенос электронов с участием молекулярного кислорода (цикл «вода – вода»). Показано, что достаточно сильное закисление цитозоля (pHcyt < 7) уменьшает отток электронов от ФС I (нециклический и псевдоциклический электронный транспорт) и стимулирует циклический перенос электронов вокруг ФС I, а также ослабляет скорость pH-зависимого синтеза ATP.

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