Zsiros Otto, Allakhverdiev Suleyman I, Higashi Shoichi, Watanabe Masakatsu, Nishiyama Yoshitaka, Murata Norio
National Institute for Basic Biology, Okazaki 444-8585, Japan.
Biochim Biophys Acta. 2006 Feb;1757(2):123-9. doi: 10.1016/j.bbabio.2006.01.004. Epub 2006 Jan 30.
When organisms that perform oxygenic photosynthesis are exposed to strong visible or UV light, inactivation of photosystem II (PSII) occurs. However, such organisms are able rapidly to repair the photoinactivated PSII. The phenomenon of photoinactivation and repair is known as photoinhibition. Under normal laboratory conditions, the rate of repair is similar to or faster than the rate of photoinactivation, preventing the detailed analysis of photoinactivation and repair as separate processes. We report here that, using strong UV-A light from a laser, we were able to analyze separately the photoinactivation and repair of photosystem II in the cyanobacterium Synechocystis sp. PCC 6803. Very strong UV-A light at 364 nm and a photon flux density of 2600 micromol photons m(-2) s(-1) inactivated the oxygen-evolving machinery and the photochemical reaction center of PSII within 1 or 2 min before the first step in the repair process, namely, the degradation of the D1 protein, occurred. During subsequent incubation of cells in weak visible light, the activity of PSII recovered fully within 30 min and this process depended on protein synthesis. During subsequent incubation of cells in darkness for 60 min, the D1 protein of the photoinactivated PSII was degraded. Further incubation in weak visible light resulted in the rapid restoration of the activity of PSII. These observations suggest that very strong UV-A light is a useful tool for the analysis of the repair of PSII after photoinactivation.
当进行氧光合作用的生物体暴露于强光或紫外光下时，光系统II（PSII）会发生失活。然而，这类生物体能够迅速修复光失活的PSII。光失活和修复的现象被称为光抑制。在正常实验室条件下，修复速率与光失活速率相似或更快，这使得无法将光失活和修复作为单独的过程进行详细分析。我们在此报告，利用来自激光的强紫外-A光，我们能够分别分析集胞藻PCC 6803中光系统II的光失活和修复过程。在修复过程的第一步（即D1蛋白降解）发生之前，364nm的极强紫外-A光和2600微摩尔光子·米⁻²·秒⁻¹的光子通量密度在1或2分钟内使PSII的放氧机制和光化学反应中心失活。在随后将细胞置于弱可见光下孵育期间，PSII的活性在30分钟内完全恢复，且此过程依赖于蛋白质合成。在随后将细胞置于黑暗中孵育60分钟期间，光失活的PSII中的D1蛋白被降解。在弱可见光下进一步孵育导致PSII活性迅速恢复。这些观察结果表明，极强紫外-A光是分析光失活后PSII修复的有用工具。
