GTP bound to chloroplast thylakoid membranes is required for light-induced, multienzyme degradation of the photosystem II D1 protein.
GTP bound to chloroplast thylakoid membranes is required for light-induced, multienzyme degradation of the photosystem II D1 protein.
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光诱导的光系统 II D1 蛋白多酶降解需要与叶绿体类囊体膜结合的 GTP。
DOI：
10.1073/pnas.96.11.6547
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发表时间：
1999
影响因子：
11.1
通讯作者：
B. Andersson
中科院分区：
文献类型：
--
作者：
C. Spetea;T. Hundal;F. Lohmann;B. Andersson
尽管光是光合作用的驱动力，但它也可能对植物有害。水分解光系统II是这种光胁迫的主要目标，导致光合电子传递失活和光氧化损伤其反应中心。植物通过复杂的修复机制存活，包括蛋白水解降解和光损伤反应中心D1蛋白的替换。基于分离的叶绿体类囊体膜和光系统II核心复合物的实验，我们报道了D1蛋白快速周转的几个方面。(i)主要裂解步骤是gtp依赖过程，导致一个23 kda n端片段的积累。（ii）不可水解的GTP类似物和apyrase处理抑制D1蛋白的蛋白水解低于基础水平，表明内源性GTP与类囊体膜紧密结合。结合研究证实了这种可能性。（iii） 23-kDa初级降解片段的蛋白水解（但不包括D1蛋白）是ATP和锌依赖的过程。（iv） D1蛋白降解是一个涉及战略（初级）蛋白酶和清理（次级）蛋白酶的多酶事件。(v)叶绿体FtsH蛋白酶可能参与次级降解步骤。除了对理解光抑制修复的意义外，紧密结合GTP的发现应该对与光合膜相关的其他调节反应和信号转导途径具有普遍意义。
Even though light is the driving force in photosynthesis, it also can be harmful to plants. The water-splitting photosystem II is the main target for this light stress, leading to inactivation of photosynthetic electron transport and photooxidative damage to its reaction center. The plant survives through an intricate repair mechanism involving proteolytic degradation and replacement of the photodamaged reaction center D1 protein. Based on experiments with isolated chloroplast thylakoid membranes and photosystem II core complexes, we report several aspects concerning the rapid turnover of the D1 protein. (i) The primary cleavage step is a GTP-dependent process, leading to accumulation of a 23-kDa N-terminal fragment. (ii) Proteolysis of the D1 protein is inhibited below basal levels by nonhydrolyzable GTP analogues and apyrase treatment, indicating the existence of endogenous GTP tightly bound to the thylakoid membrane. This possibility was corroborated by binding studies. (iii) The proteolysis of the 23-kDa primary degradation fragment (but not of the D1 protein) is an ATP- and zinc-dependent process. (iv) D1 protein degradation is a multienzyme event involving a strategic (primary) protease and a cleaning-up (secondary) protease. (v) The chloroplast FtsH protease is likely to be involved in the secondary degradation steps. Apart from its significance for understanding the repair of photoinhibition, the discovery of tightly bound GTP should have general implications for other regulatory reactions and signal transduction pathways associated with the photosynthetic membrane.