Identification of genes encoding photoconvertible (Class I) water-soluble chlorophyll-binding proteins from <i>Chenopodium ficifolium</i>
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Photoconvertible water-soluble chlorophyll-binding proteins, called Class I WSCPs, have been detected in Chenopodiaceae, Amaranthaceae and Polygonaceae plant species. To date, <i>Chenopodium album WSCP</i> (<i>CaWSCP</i>) is the only cloned gene encoding a Class I WSCP. In this study, we identified two cDNAs encoding <i>Chenopodium ficifolium</i> Class I WSCPs, <i>CfWSCP1</i>, and <i>CfWSCP2</i>. Sequence analyses revealed that the open reading frames of <i>CfWSCP1</i> and <i>CfWSCP2</i> were 585 and 588 bp, respectively. Furthermore, both CfWSCPs contain cystein2 and cystein30, which are essential for the chlorophyll-binding ability of CaWSCP. Recombinant CfWSCP1 and CfWSCP2, expressed in <i>Escherichia coli</i> as hexa-histidine fusion proteins (CfWSCP1-His and CfWSCP2-His), formed inclusion bodies; however, we were able to solubilize these using a buffer containing 8 M urea and then refold them by dialysis. The refolded CfWSCP1-His and CfWSCP2-His could bind chlorophylls and exhibited photoconvertibility, confirming that the cloned CfWSCPs are further examples of Class I WSCPs.
光可逆水溶性叶绿素结合蛋白（Photoconvertible water-soluble chlorophyll-binding proteins）又称I类水溶性叶绿素结合蛋白（Class I WSCPs），已在藜科（Chenopodiaceae）、苋科（Amaranthaceae）和蓼科（Polygonaceae）植物中被检测到。截至目前，仅克隆得到了编码I类WSCP的藜（Chenopodium album）WSCP（CaWSCP）基因。本研究中，我们鉴定得到两个编码细叶藜（Chenopodium ficifolium）I类WSCP的cDNA，分别为CfWSCP1与CfWSCP2。序列分析显示，CfWSCP1与CfWSCP2的开放阅读框长度分别为585 bp与588 bp。此外，两种CfWSCP均含有半胱氨酸2与半胱氨酸30位点，该位点是CaWSCP叶绿素结合能力的必需结构基础。以六组氨酸融合蛋白（CfWSCP1-His与CfWSCP2-His）形式在大肠杆菌（Escherichia coli）中表达的重组CfWSCP1与CfWSCP2均形成了包涵体，但我们可通过含8 M尿素的缓冲液对其进行溶解，并经透析实现复性。复性后的CfWSCP1-His与CfWSCP2-His可结合叶绿素并表现出光可逆性，证实本次克隆得到的CfWSCP均为I类WSCP的又一典型例证。
