Reinbothe Christiane, Satoh Hiroyuki, Alcaraz Jean-Pierre, Reinbothe Steffen
Lehrstuhl für Pflanzenphysiologie, Universität Bayreuth, D-95447 Bayreuth, Germany.
Plant Physiol. 2004 Apr;134(4):1355-65. doi: 10.1104/pp.103.033613. Epub 2004 Mar 26.
All chlorophyll (Chl)-binding proteins involved in photosynthesis of higher plants are hydrophobic membrane proteins integrated into the thylakoids. However, a different category of Chl-binding proteins, the so-called water-soluble Chl proteins (WSCPs), was found in members of the Brassicaceae, Polygonaceae, Chenopodiaceae, and Amaranthaceae families. WSCPs from different plant species bind Chl a and Chl b in different ratios. Some members of the WSCP family are induced after drought and heat stress as well as leaf detachment. It has been proposed that this group of proteins might have a physiological function in the Chl degradation pathway. We demonstrate here that a protein that shared sequence homology to WSCPs accumulated in etiolated barley (Hordeum vulgare) seedlings exposed to light for 2 h. The novel 22-kD protein was attached to the outer envelope of barley etiochloroplasts, and import of the 27-kD precursor was light dependent and induced after feeding the isolated plastids the tetrapyrrole precursor 5-aminolevulinic acid. HPLC analyses and spectroscopic pigment measurements of acetone-extracted pigments showed that the 22-kD protein is complexed with chlorophyllide. We propose a novel role of WSCPs as pigment carriers operating during light-induced chloroplast development.
所有参与高等植物光合作用的叶绿素（Chl）结合蛋白都是整合到类囊体中的疏水膜蛋白。然而，在十字花科、蓼科、藜科和苋科植物中发现了另一类叶绿素结合蛋白，即所谓的水溶性叶绿素蛋白（WSCPs）。来自不同植物物种的WSCPs以不同比例结合叶绿素a和叶绿素b。WSCP家族的一些成员在干旱、热胁迫以及叶片脱离后被诱导产生。有人提出，这组蛋白可能在叶绿素降解途径中具有生理功能。我们在此证明，一种与WSCPs具有序列同源性的蛋白在黄化大麦（Hordeum vulgare）幼苗光照2小时后积累。这种新的22-kD蛋白附着在大麦黄化叶绿体的外膜上，27-kD前体的导入依赖光照，并在给分离的质体提供四吡咯前体5-氨基乙酰丙酸后被诱导。对丙酮提取色素的HPLC分析和光谱色素测量表明，22-kD蛋白与叶绿素酸酯复合。我们提出WSCPs作为在光诱导叶绿体发育过程中起作用的色素载体的新作用。
