A heat shock protein localized to chloroplasts is a member of a eukaryotic superfamily of heat shock proteins.
A heat shock protein localized to chloroplasts is a member of a eukaryotic superfamily of heat shock proteins.
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定位于叶绿体的热休克蛋白是热休克蛋白真核超家族的成员。
作者：
E. Vierling;R. T. Nagao;A. DeRocher;Lisa M. Harris
我们已经从大豆和豌豆中分离到了定位于叶绿体的核编码的热休克蛋白(HSPs)的cDNA克隆。这些热休克蛋白的mRNAs在控制温度下是检测不到的，但在2小时的热休克中增加了大约150倍。杂交选择和体外翻译表明，这些热休克蛋白是作为前体蛋白合成的，在输入到分离的叶绿体过程中经过5-6.5kd的去除进行加工。核苷酸序列分析表明，豌豆和大豆成熟蛋白衍生的氨基酸序列有79%的同源性。虽然豌豆cDNA编码的转运肽具有一些典型的转运肽序列特征，包括高Ser含量、多个碱性残基和无酸性残基，但它缺少对其他叶绿体蛋白的输入和成熟至关重要的两个结构域。叶绿体热休克蛋白的羧基末端区域与大豆和其他真核生物的细胞质热休克蛋白有显著的同源性。我们推测，叶绿体热休克蛋白具有一个共同的结构和功能结构域，其摩尔分数较低。WT热休克蛋白定位于细胞的其他部分，可能是从核基因进化而来的。
We have isolated cDNA clones from soybean and pea that specify nuclear‐encoded heat shock proteins (HSPs) which localize to chloroplasts. The mRNAs for these HSPs are undetectable at control temperatures, but increase approximately 150‐fold during a 2‐h heat shock. Hybridization‐selection followed by in vitro translation demonstrates that these HSPs are synthesized as precursor proteins which are processed by the removal of 5‐6.5 kd during import into isolated chloroplasts. The nucleotide sequence of the cDNAs shows the derived amino acid sequences of the mature pea and soybean proteins are 79% identical. While the predicted transit peptide encoded by the pea cDNA has some characteristics typical of transit sequences, including high Ser content, multiple basic residues and no acidic residues, it lacks two domains proposed to be important for import and maturation of other chloroplast proteins. The carboxy‐terminal region of the chloroplast HSP has significant homology to cytoplasmic HSPs from soybean and other eukaryotes. We hypothesize that the chloroplast HSP shares a common structural and functional domain with low mol. wt HSPs which localize to other parts of the cell, and may have evolved from a nuclear gene.