LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells
LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells
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DOI：
10.1073/pnas.1605380113
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发表时间：
2016-07-05
影响因子：
11.1
通讯作者：
Croce, Roberta
中科院分区：
文献类型：
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作者：
Dinc, Emine;Tian, Lijin;Croce, Roberta
为了避免光损伤，光合生物能够在一个被称为非光化学猝灭（NPQ）的过程中热耗散吸收过多的能量。虽然NPQ已被广泛研究，但主要参与者和猝灭机制仍存在争议。这是由于很难从体内实验中提取分子信息，以及缺乏体外实验的验证系统。在这里，我们创造了一个最小的绿藻莱茵衣藻细胞，它能够经历NPQ。我们发现藻类的主要光收集复合物LHCII本身不能在pH变化时切换到淬灭构象。相反，少量的蛋白质LHCSR1（光捕获复杂应力相关1）能够在含有lhcii的膜中诱导一个大的、快速的、可逆的ph依赖性猝灭。这些结果强烈表明LHCSR1作为pH传感器，它调节了大量LHCII的激发态寿命，也解释了在LHCSR3-less突变体中观察到的NPQ。讨论了可能的淬火机理。
To avoid photodamage, photosynthetic organisms are able to thermally dissipate the energy absorbed in excess in a process known as nonphotochemical quenching (NPQ). Although NPQ has been studied extensively, the major players and the mechanism of quenching remain debated. This is a result of the difficulty in extracting molecular information from in vivo experiments and the absence of a validation system for in vitro experiments. Here, we have created a minimal cell of the green alga Chlamydomonas reinhardtii that is able to undergo NPQ. We show that LHCII, the main light harvesting complex of algae, cannot switch to a quenched conformation in response to pH changes by itself. Instead, a small amount of the protein LHCSR1 (light-harvesting complex stress related 1) is able to induce a large, fast, and reversible pH-dependent quenching in an LHCII-containing membrane. These results strongly suggest that LHCSR1 acts as pH sensor and that it modulates the excited state lifetimes of a large array of LHCII, also explaining the NPQ observed in the LHCSR3-less mutant. The possible quenching mechanisms are discussed.