Light-Harvesting Chlorophyll a/b Complexes: Interdependent Pigment Synthesis and Protein Assembly.
Light-Harvesting Chlorophyll a/b Complexes: Interdependent Pigment Synthesis and Protein Assembly.
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DOI：
10.1105/tpc.7.6.689
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发表时间：
1995-06
期刊：
影响因子：
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通讯作者：
F. Plumley;Gregory W. Schmidt
中科院分区：
文献类型：
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作者：
F. Plumley;Gregory W. Schmidt
本文分析了两种具有低水平Chl B、新黄质和氯黄质的衣原体核突变体的捕光叶绿素（Chl）a/B蛋白（LHCP）和天线色素的生物遗传相互依赖性。在突变体PA2.1中，主要捕光复合物LHC II的载脂蛋白前体（pLHCP II）以近似野生型的速率合成，加工至其成熟大小，并迅速降解。由于大部分不稳定的LHCP II在PA2.1是可溶的，类囊体整合因子显然是有缺陷的，在这个菌株。叶绿素a、叶绿素B、新黄质和氯黄质的合成和积累在PA 2.1中协同减少，表明LHCP II在这些色素的从头合成中起重要的调节或底物作用。突变体GE 2.27主要在Chl B合成中受损，但仍然积累了所有LHCP的野生型水平。拓扑结构的研究表明，GE2.27 LHCP II插入类囊体是不完整的，即使他们没有改变结构。因此，Chl B形成介导类囊体整合启动后LHCP II的构象变化。GE 2.27还表现出非常低的新黄质合成速率，并且不能积累氯黄质。具有不同Chl B形成能力的回复突变体GE 2.27菌株提供了新黄质合成和积累与LHCP II整合到类囊体中的最后步骤耦合的额外证据。我们建议，LHC的生物起源包括相互依存的色素合成/组装事件，发生在LHCP整合到类囊体膜和缺陷，在这些事件中的多效性的特点，许多叶绿素b缺陷突变体。
The biogenetic interdependence of light-harvesting chlorophyll (Chl) a/b proteins (LHCPs) and antenna pigments has been analyzed for two nuclear mutants of Chlamydomonas that have low levels of Chl b, neoxanthin, and loroxanthin. In mutant PA2.1, the apoprotein precursors (pLHCP II) of the major light-harvesting complex LHC II were synthesized at approximately wild-type rates, processed to their mature size, and rapidly degraded. Because the bulk of labile LHCP II in PA2.1 was soluble, a thylakoid integration factor apparently is defective in this strain. Chl a, Chl b, neoxanthin, and loroxanthin synthesis and accumulation were coordinately reduced in PA2.1, indicating that LHCP II play important regulatory or substrate roles in de novo synthesis of these pigments. Mutant GE2.27 is impaired principally in Chl b synthesis but nonetheless accumulated wild-type levels of all LHCPs. Topology studies of the GE2.27 LHCP II demonstrated that their insertion into thylakoids was incomplete even though they were not structurally altered. Thus, Chl b formation mediates conformational changes of LHCP II after thylakoid integration is initiated. GE2.27 also exhibited very low rates of neoxanthin synthesis and was unable to accumulate loroxanthin. Revertant GE2.27 strains with varying capacities for Chl b formation provided additional evidence that neoxanthin synthesis and accumulation are coupled with the final steps of LHCP II integration into thylakoids. We propose that biogenesis of LHC includes interdependent pigment synthesis/assembly events that occur during LHCP integration into the thylakoid membrane and that defects in these events account for the pleiotropic characteristics of many Chl b-deficient mutants.