The DnaJ-Like Zinc-Finger Protein HCF222 Is Required for Thylakoid Membrane Biogenesis in Plants1[OPEN]
The DnaJ-Like Zinc-Finger Protein HCF222 Is Required for Thylakoid Membrane Biogenesis in Plants1[OPEN]
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DOI：
10.1104/pp.17.00401
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发表时间：
2017-07-01
期刊：
影响因子：
7.4
通讯作者：
Meierhoff, Karin
中科院分区：
文献类型：
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作者：
Hartings, Stephanie;Paradies, Susanne;Meierhoff, Karin
为了了解高等植物类囊体膜的生物发生，并确定建立这种高度复杂的膜系统所需的辅助蛋白，我们已经确定了等位基因核突变体高叶绿素荧光-222-1（hcf 222 -1）和hcf 222 -2，并分离的致病基因的图位克隆。在甲磺酸乙酯诱导的突变体hcf 222 -1中，细胞色素B（6）f（Cytb 6 f）复合物的积累与野生型相比减少至30%。其他类囊体膜复合物积累到正常水平。T-DNA敲除突变体hcf 222 -2表现出更严重的缺陷，相对于类囊体膜蛋白和积累只有10%的Cytb 6 f复合物，伴随着减少光系统II，光系统II捕光复合物，和光系统I。HCF 222编码拟南芥中的99个氨基酸的蛋白质，其与DnaJ分子伴侣的富含半胱氨酸的锌结合结构域具有相似性。胰岛素沉淀试验证明HCF 222在体外具有二硫键还原酶活性。该蛋白质在高等植物和硅藻中是保守的，但在藻类和蓝藻中不存在。共聚焦荧光显微镜显示，HCF 222-绿色荧光蛋白的一部分是可检测到的内质网，但它也可以识别叶绿体。HCF 222的融合构建体含有质体转运肽，靶向蛋白质进入叶绿体，并能够弥补突变缺陷。这些研究结果表明，叶绿体靶向的HCF 222是必不可少的成熟和/或组装的Cytb 6 f复合物，并很可能参与巯基-二硫键生物化学在类囊体膜。
To understand the biogenesis of the thylakoid membrane in higher plants and to identify auxiliary proteins required to build up this highly complex membrane system, we have characterized the allelic nuclear mutants high chlorophyll fluorescence-2221 (hcf222-1) and hcf222-2 and isolated the causal gene by map-based cloning. In the ethyl methanesulfonate-induced mutant hcf222-1, the accumulation of the cytochrome b(6)f (Cytb6f) complex was reduced to 30% compared with the wild type. Other thylakoid membrane complexes accumulated to normal levels. The T-DNA knockout mutant hcf222-2 showed a more severe defect with respect to thylakoid membrane proteins and accumulated only 10% of the Cytb6f complex, accompanied by a reduction in photosystem II, the photosystem II light-harvesting complex, and photosystem I. HCF222 encodes a protein of 99 amino acids in Arabidopsis (Arabidopsis thaliana) that has similarities to the cysteine-rich zinc-binding domain of DnaJ chaperones. The insulin precipitation assay demonstrated that HCF222 has disulfide reductase activity in vitro. The protein is conserved in higher plants and bryophytes but absent in algae and cyanobacteria. Confocal fluorescence microscopy showed that a fraction of HCF222-green fluorescent protein was detectable in the endoplasmic reticulum but that it also could be recognized in chloroplasts. A fusion construct of HCF222 containing a plastid transit peptide targets the protein into chloroplasts and was able to complement the mutational defect. These findings indicate that the chloroplast-targeted HCF222 is indispensable for the maturation and/or assembly of the Cytb6f complex and is very likely involved in thiol-disulfide biochemistry at the thylakoid membrane.