Structural mechanism and photoprotective function of water-soluble chlorophyll-binding protein
Structural mechanism and photoprotective function of water-soluble chlorophyll-binding protein
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DOI：
10.1074/jbc.m609458200
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发表时间：
2007-03-02
影响因子：
4.8
通讯作者：
Uchida, Akira
中科院分区：
文献类型：
--
作者：
Horigome, Daisuke;Satoh, Hiroyuki;Uchida, Akira
水溶性叶绿素结合蛋白（water-soluble chlorophyll-binding protein， WSCP）是绿色植物中唯一已知的叶绿素载体。近年来，通过EPR测量证实了WSCP的光保护功能；在WSCP四聚体中，光诱导的Chl单重态氧的形成比未结合的Chl低约4倍。本文报道了从维根胡椒草（Lepidium virginicum）叶中纯化的WSCP-Chl复合物的晶体结构，以阐明其光保护作用的机制。WSCP-Chl复合物是一种同型四聚体，由180个氨基酸组成的4条蛋白质链和4个Chl分子组成。在复合物的中心形成了一个疏水腔，其中所有四个Chl分子被紧密包裹并与散装溶剂隔离。结合新的Chl结合模式，我们提出光保护机制可能是基于抑制Chl分子与分子氧之间的物理接触。
A water-soluble chlorophyll-binding protein (WSCP) is the single known instance of a putative chlorophyll (Chl) carrier in green plants. Recently the photoprotective function of WSCP has been demonstrated by EPR measurements; the light-induced singlet-oxygen formation of Chl in the WSCP tetramer is about four times lower than that of unbound Chl. This paper describes the crystal structure of the WSCP-Chl complex purified from leaves of Lepidium virginicum (Virginia pepperweed) to clarify the mechanism of its photoprotective function. The WSCP-Chl complex is a homotetramer comprising four protein chains of 180 amino acids and four Chl molecules. At the center of the complex one hydrophobic cavity is formed in which all of the four Chl molecules are tightly packed and isolated from bulk solvent. With reference to the novel Chl-binding mode, we propose that the photoprotection mechanism may be based on the inhibition of physical contact between the Chl molecules and molecular oxygen.