Alric Jean, Lavergne Jérôme, Rappaport Fabrice
UMR 7141, CNRS et Université Pierre et Marie Curie (Paris VI), Institut de Biologie Physico-Chimique, 13 Rue Pierre et Marie Curie 75005 Paris, France.
Biochim Biophys Acta. 2010 Jan;1797(1):44-51. doi: 10.1016/j.bbabio.2009.07.009. Epub 2009 Aug 3.
Assimilation of atmospheric CO2 by photosynthetic organisms such as plants, cyanobacteria and green algae, requires the production of ATP and NADPH in a ratio of 3:2. The oxygenic photosynthetic chain can function following two different modes: the linear electron flow which produces reducing power and ATP, and the cyclic electron flow which only produces ATP. Some regulation between the linear and cyclic flows is required for adjusting the stoichiometric production of high-energy bonds and reducing power. Here we explore, in the green alga Chlamydomonas reinhardtii, the onset of the cyclic electron flow during a continuous illumination under aerobic conditions. In mutants devoid of Rubisco or ATPase, where the reducing power cannot be used for carbon fixation, we observed a stimulation of the cyclic electron flow. The present data show that the cyclic electron flow can operate under aerobic conditions and support a simple competition model where the excess reducing power is recycled to match the demand for ATP.
植物、蓝细菌和绿藻等光合生物对大气中二氧化碳的同化作用需要以3:2的比例产生ATP和NADPH。产氧光合链可以通过两种不同模式发挥作用：产生还原力和ATP的线性电子流，以及仅产生ATP的循环电子流。为了调节高能键和还原力的化学计量产生，线性和循环流之间需要一些调节。在这里，我们在绿藻莱茵衣藻中探索了在有氧条件下持续光照期间循环电子流的起始。在缺乏Rubisco或ATPase的突变体中，还原力不能用于碳固定，我们观察到循环电子流受到刺激。目前的数据表明，循环电子流可以在有氧条件下运行，并支持一个简单的竞争模型，即过量的还原力被循环利用以匹配对ATP的需求。
