Braun G, Evron Y, Malkin S, Avron M
Department of Biochemistry, Weizmann Institute of Science, Rehovot, Israel.
FEBS Lett. 1991 Mar 11;280(1):57-60. doi: 10.1016/0014-5793(91)80203-f.
The involvement of ATP synthase in the imbalance between the photoactivities of PS I and PS II under light-limiting conditions, was examined in broken lettuce chloroplasts using modulated fluorimetry. The imbalance, in favor of PS II, was minimal and roughly constant between pH 6.5-7.3 (ratio of PS II/PS I activities about 1.1), and maximal at pH 8.5 (ratio of PS II/PS I activities about 1.4). This increase was strongly inhibited by a treatment of the chloroplasts with the CF0 ATP synthase inhibitor DCCD, but unaffected by the CF1 ATPase inhibitor, tentoxin. However, tentoxin plus ADP-P1 did inhibit the high pH-induced increased imbalance. These results, when considered with the previous results on the effect of high pH on proton flux through the ATP synthase, suggest that the rate of such proton flow controls the imbalance between the two photo-systems. It is possible that there is an in vivo fine-tuning regulating mechanism of the photosystems imbalance via the opening and closing of proton gradient dissipation through the ATP synthase. This mechanism may help alleviate photoinhibitory damage.
利用调制荧光法，在破碎的生菜叶绿体中研究了ATP合酶在光限制条件下对光系统I（PS I）和光系统II（PS II）光活性失衡的影响。有利于PS II的失衡在pH 6.5 - 7.3之间最小且大致恒定（PS II/PS I活性比约为1.1），在pH 8.5时最大（PS II/PS I活性比约为1.4）。用CF0 ATP合酶抑制剂二环己基碳二亚胺（DCCD）处理叶绿体可强烈抑制这种增加，但不受CF1 ATP酶抑制剂抗霉素A的影响。然而，抗霉素A加ADP-P1确实抑制了高pH诱导的失衡增加。这些结果与先前关于高pH对通过ATP合酶的质子通量影响的结果相结合，表明这种质子流速率控制着两个光系统之间的失衡。有可能存在一种通过ATP合酶质子梯度消散的开放和关闭来对光系统失衡进行体内微调的调节机制。这种机制可能有助于减轻光抑制损伤。
