The photosynthetic electron transfer chain generates proton motive force (pmf), composed of both electric field (Deltapsi) and concentration (DeltapH) gradients. Both components can drive ATP synthesis, whereas the DeltapH component alone can trigger feedback regulation of the antenna. It has often been suggested that a relatively large pmf is needed to sustain the energetic contributions of the ATP synthase reaction (DeltaG(ATP)), and that the Deltapsi component is dissipated during illumination, leading to an acidic lumen in the light. We suggest that this is incompatible with the stabilities of lumenal components and the observed activation of downregulation. Recent work on the chloroplast ATP synthase suggests that a more moderate pmf can sustain DeltaG(ATP). In addition, in vivo probes suggest that a substantial fraction of pmf can be stored as Deltapsi. Together, these factors should allow sufficient DeltaG(ATP) to maintain lumen pH in a range where lumenal enzyme activities are nearly optimal, and where the level of NPQ is regulated.

中文翻译：

---

平衡类囊体质子梯度的中心作用。

光合电子转移链产生质子原动力（pmf），由电场（Deltapsi）和浓度（DeltapH）梯度组成。这两种成分都可以驱动ATP合成，而单独的DeltapH成分可以触发天线的反馈调节。经常有人建议，需要相对较大的pmf来维持ATP合酶反应（DeltaG（ATP））的能量作用，并且在照明过程中会消散Deltapsi成分，从而在光照下产生酸性内腔。我们建议这与腔组件的稳定性和下调的激活不兼容。叶绿体ATP合酶的最新研究表明，更适度的pmf可以维持DeltaG（ATP）。此外，体内探针表明，大部分pmf可以Deltapsi的形式存储。这些因素加在一起，应使足够的DeltaG（ATP）维持管腔pH值在管腔酶活性几乎最佳且NPQ水平受到调节的范围内。