The regulatory mechanisms for maintaining the chlorophyll to apoproteins ratio.

维持叶绿素与脱辅基蛋白比例的调节机制。

基本信息

批准号：
02640520
负责人：
TANAKA Ayumi
金额：
$ 1.15万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

When etiolated seedlings are illuminated,chlorophyll(Chl)begins to be synthesized with accumulation of Chl-protein complex(CP)apoproteins. Newly synthesized Chl is incorporated into apoproteins to form CPs,which are associated with other components to form functional photosystems.Each CP is supposed to be composed of Chl and its apoprotein in a definite ratio. It have been shown that light-harvesting Chl a/b-protein complex of PSII binds 15 Chl. The Chl/P700 ratio for P700-Chl a-protein complex isolated by SDS-PAGE was reported to be 120. Two apoproteins of PSII core have definite ratios of Chl to apoproteins Taking into consideration the observation that all the Chl molecules bind to apoproteins in thylakoid membranes,these indicate that the ratio of Chl to apoproteins of mature chloroplasts would be kept constant.Accumulation of excess Chl or apoproteins which do not bind with each other would not be favorable for chloroplasts. The accumulation of apoproteins must be regulated in accordance with changes in the rate of Chl synthesis. We focussed our attention on the regulatory mechanisms operate to maintain the Chl to apoprotein ratio constant during chloroplast development and the followings were elucidated.(1)Chl is supplied to apoproteins in two ways:by distribution of newly synthesized Chl and by redistribution of Chl that have been previously incorporated into other CPs. (2)The formation of different CPs is regulated by differential affinities of the apoproteins for Chl.(3)Coordinate accumulation of Chl and apoproteins of CPs is achieved through rapid digestion of apoproteins which are not bound with Chl.

当黄化幼苗受到光照时，叶绿素（Chl）开始合成，并积累叶绿素蛋白复合物（CP）脱辅基蛋白。新合成的叶绿素与脱辅基蛋白结合形成CP，与其他成分结合形成功能性光系统。每个CP应该由叶绿素及其脱辅基蛋白按一定比例组成。研究表明，PSII 的光捕获叶绿素 a/b 蛋白复合物可结合 15 个叶绿素。据报道，通过 SDS-PAGE 分离的 P700-Chl a 蛋白复合物的 Chl/P700 比率为 120。PSII 核心的两个脱辅基蛋白具有明确的 Chl 与脱辅基蛋白比例。考虑到观察到所有 Chl 分子都与脱辅基蛋白结合，类囊体膜，这表明成熟叶绿体的叶绿素与脱辅基蛋白的比例将保持恒定。过量叶绿素的积累或彼此不结合的脱辅基蛋白对叶绿体不利。脱辅基蛋白的积累必须根据叶绿素合成速率的变化进行调节。我们将注意力集中在叶绿体发育过程中维持叶绿素与脱辅基蛋白比例恒定的调节机制上，并阐明了以下内容。（1）叶绿素通过两种方式提供给脱辅基蛋白：通过新合成的叶绿素的分配和叶绿素的重新分配之前已合并到其他 CP 中。 (2)不同CP的形成是通过脱辅基蛋白对叶绿素的不同亲和力来调节的。(3)通过快速消化未与叶绿素结合的脱辅基蛋白来实现叶绿素和CP的脱辅基蛋白的协同积累。