Occupation of the Q(B)-binding pocket by a photosystem II inhibitor triggers dark cleavage of the D1 protein subjected to brief preillumination
Occupation of the Q(B)-binding pocket by a photosystem II inhibitor triggers dark cleavage of the D1 protein subjected to brief preillumination
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DOI：
10.1074/jbc.271.29.17383
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发表时间：
1996-07-19
影响因子：
4.8
通讯作者：
Ono, T
中科院分区：
文献类型：
--
作者：
Nakajima, Y;Yoshida, S;Ono, T
光系统II反应中心的D1蛋白质通过其选择性和特异性的切割以光依赖的方式非常迅速地翻转。以PS Ⅱ抑制剂N-辛基-3-硝基-2，4，6-三羟基苯甲酰胺（PNO 8）为探针，研究了D1的裂解。获得了以下结果。(i)D1被选择性地切割成23 kDa的N-末端和9 kDa的C-末端片段在完全黑暗中由PNO 8在一个单一的网站在一个D-E环连接跨膜螺旋D和E，（ii）切割显着增强PS II时被照亮了一段短暂的时间之前，在黑暗中加入PNO 8。(iii)在黑暗中孵育期间，预照射的效果缓慢丧失，在25 ℃下衰变半衰期类似于1小时。(iv)裂解所需的预光照强度远低于O-2释放所需的预光照强度。(v)光引发的分裂D1观察类囊体，PS II膜，PS II核心颗粒，但不是在纯化的PS II反应中心。超过60%的D1被切割成两个片段，没有其他副产物。(vi)裂解反应揭示了一个显着的pH依赖性，这是相当不同的PS II活性的抑制。结果被解释为指示PNO 8与Q（B）结合口袋的结合触发了先前在照明期间被修饰的D1的蛋白水解裂解。
The D1 protein of the photosystem (PS) II reaction center turns over very rapidly in a light-dependent man ner initiated by its selective and specific cleavage. The cleavage of D1 was studied by using a PS II inhibitor, N-octyl-3-nitro-2,4,6-trihydroxybenzamide (PNO8), as a molecular probe. The following results were obtained. (i) D1 was selectively cleaved into 23-kDa N-terminal and 9-kDa C-terminal fragments in complete darkness by PNO8 at a single site in a D-E loop connecting membrane-spanning helices D and E, (ii) The cleavage was markedly enhanced when PS II was illuminated for a brief period before the addition of PNO8 in darkness. (iii) The effect of preillumination was slowly lost during incubation in the dark, with a decay half-time of similar to 1 h at 25 degrees C. (iv) The light intensity of preillumination required for the cleavage was much lower than that required for O-2 evolution. (v) The light-triggered cleavage of D1 was observed in thylakoids, PS II membranes, and PS II core particles, but not in purified PS II reaction centers. More than 60% of D1 was cleaved into the two fragments with no other by-products. (vi) The cleavage reaction revealed a marked pH dependence that was considerably different from that for inhibition of PS II activity. The results are interpreted as indicating that the binding of PNO8 to the Q(B)-binding pocket triggers proteolytic cleavage of D1 that has been previously modified during illumination.