【摘要】 光系统Ⅱ反应中心Ｄ１／Ｄ２／Ｃｙｔ ｂ５５９ 复合物对光照十分敏感。不仅色素分子，而且多肽链上的氨基酸残基（如组氨酸和甲硫氨酸）均会受到破坏。光照同时引起Ｄ１ 和Ｄ２ 蛋白的降解。在ＳＤＳ聚丙烯酰胺多肽电泳图谱上，Ｄ１／Ｄ２ 二聚体的含量增多，同时有一条分子量大约为４１ ｋＤ的新带出现。在光照后的暗放置过程中，氨基酸组成不再变化，但Ｄ１ 和Ｄ２ 蛋白的降解及大分子量片段的产生仍继续进行。对组氨酸和甲硫氨酸的破坏与Ｄ１、Ｄ２ 蛋白的降解关系进行了初步的分析，推测在光破坏过程中，Ｄ１ 和Ｄ２ 蛋白也许发生了化学断裂和共价交联作用更多还原

【Abstract】 Photosystem Ⅱ reaction center D1/D2/Cyt b559 complex is very sensitive to light. Besides pigments, some amino acids, like histidine and methionine residues on the polypeptide chain, were damaged and D1 and D2 proteins were degraded by illumination. SDS PAGE analysis demonstrated an increased content of the D1 and D2 protein dimers and a new band with molecular weight of 41 kD after light treatment. Meanwhile, the D1 and D2 bands were shifted to apparent positions of higher molecular weight. During the consequent incubation in the dark following illumination, although there was no change in the composition of amino acids, the degradation process of D1 and D2 proteins and the production of 41 kD fragment continued. It was proposed that degradation of D1 and D2 proteins was probably due to the photodamage of some amino acids via chemical splitting and co valent cross linkage in this process.更多还原