Cyclic electron flow (CEF) around photosystem I is vital to balancing the photosynthetic energy budget of cyanobacteria and other photosynthetic organisms. The coupling of CEF to proton pumping has long been hypothesized to occur, providing proton motive force (PMF) for the synthesis of ATP with no net cost to [NADPH]. This is thought to occur largely through the activity of NDH-1 complexes, of which cyanobacteria have four with different activities. While a much work has been done to understand the steady-state PMF in both the light and dark, and fluorescent probes have been developed to observe these fluxes in vivo, little has been done to understand the kinetics of these fluxes, particularly with regard to NDH-1 complexes. To monitor the kinetics of proton pumping in Synechocystis sp. PCC 6803, the pH sensitive dye Acridine Orange was used alongside a suite of inhibitors in order to observe light-dependent proton pumping. The assay was demonstrated to measure photosynthetically driven proton pumping and used to measure the rates of proton pumping unimpeded by dark ΔpH. Here, the cyanobacterial NDH-1 complexes are shown to pump a sizable portion of proton flux when CEF-driven and LEF-driven proton pumping rates are observed and compared in mutants lacking some or all NDH-1 complexes. It is also demonstrated that PSII and LEF are responsible for the bulk of light induced proton pumping, though CEF and NDH-1 are capable of generating ~40% of the proton pumping rate when LEF is inactivated.

光系统I周围的循环电子流（CEF）对于平衡蓝细菌和其他光合生物的光合能量收支至关重要。长期以来，人们一直假设CEF与质子泵的耦合会发生，它为ATP的合成提供了质子动力（PMF），而[NADPH]却没有任何净成本。认为这主要是通过NDH-1配合物的活性而发生的，其中蓝细菌具有四种具有不同活性的配合物。尽管已经做了很多工作来了解明暗情况下的稳态PMF，并且已经开发了荧光探针来观察体内这些通量，但几乎没有做任何工作来了解这些通量的动力学，特别是对于NDH-1复合物。监测突囊藻中质子泵送的动力学sp。为了观察光依赖的质子泵浦，将pH敏感染料a啶橙PCC 6803与一系列抑制剂一起使用。证明该测定法测量光合作用驱动的质子泵送，并用于测量不受黑暗ΔpH干扰的质子泵送速率。在这里，当观察到CEF驱动和LEF驱动的质子泵送速率并在缺乏某些或全部NDH-1复合物的突变体中进行比较时，蓝藻NDH-1复合物显示出相当一部分质子通量。还证明了PSII和LEF负责光诱导的质子泵浦，尽管当LEF灭活时CEF和NDH-1能够产生约40％的质子泵浦率。