The identification of a heat-shock protein complex in chloroplasts of barley leaves.
The identification of a heat-shock protein complex in chloroplasts of barley leaves.
复制标题
大麦叶叶绿体中热休克蛋白复合物的鉴定。
作者：
A. Clarke;Christa Critchley
大麦（Hordeum vulgare L.）叶绿体蛋白的体内放射性标记cv Corvette）叶片的热休克蛋白，并通过一维电泳分离，揭示了至少7个分子量在24 ~ 94 kD之间的热休克蛋白，其中大部分以前在该C（3）种中没有鉴定过。分馏成基质和类囊体膜组件表明，所有的叶绿体热休克蛋白质合成的细胞质核糖体，易位到叶绿体，并位于基质中。通过本地（nondissociating）聚丙烯酰胺凝胶电泳检查基质制剂发现大麦中存在高分子量的热休克蛋白复合物。该复合物的大小估计为250至265 kD。变性聚丙烯酰胺凝胶电泳显示一个单一的蛋白质组分，一个32 kD的热休克蛋白。这种蛋白质的合成和热休克蛋白复合物的形成依赖于功能性胞质核糖体。免疫学研究表明，热休克蛋白复合物不包含任何蛋白质同源的α-亚基的核酮糖二磷酸羧化酶加氧酶亚基结合蛋白。该复合物的其他特征包括不含核酸（RNA或DNA）以及在Mg（2+）/ATP存在下不解离。这些结果表明，大麦叶绿体中的热激蛋白复合物是一个均匀的八聚体的32 kD亚基。
In vivo radiolabeling of chloroplast proteins in barley (Hordeum vulgare L. cv Corvette) leaves and their separation by one-dimensional electrophoresis revealed at least seven heat-shock proteins between 24 and 94 kD, of which most have not been previously identified in this C(3) species. Fractionation into stromal and thylakoid membrane components showed that all chloroplast heat-shock proteins were synthesized on cytoplasmic ribosomes, translocated into the chloroplast, and located in the stroma. Examination of stromal preparations by native (nondissociating) polyacrylamide gel electrophoresis revealed the presence of a high-molecular mass heat-shock protein complex in barley. This complex was estimated to be 250 to 265 kD in size. Dissociation by denaturing polyacrylamide gel electrophoresis revealed a single protein component, a 32-kD heat-shock protein. The synthesis of this protein and the formation of the heat-shock protein complex were dependent on functional cytoplasmic ribosomes. Immunological studies showed that the heat-shock protein complex did not contain any proteins homologous to the alpha-subunit of ribulose bisphosphate carboxylase oxygenase subunit-binding protein. Other features about the complex included the absence of nucleic acid (RNA or DNA) and its nondissociation in the presence of Mg(2+)/ATP. These results suggest that the heat-shock protein complex in barley chloroplasts is a homogeneous octamer of 32-kD subunits.