Reid B G, Flynn G C
Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene, 97403, USA.
J Biol Chem. 1996 Mar 22;271(12):7212-7. doi: 10.1074/jbc.271.12.7212.
The Escherichia coli chaperone GroEL is a member of a class of molecular chaperones that possesses a stacked double ring structure containing seven subunits per ring, with approximately 60-kDa subunits. It has been suggested that newly synthesized proteins may interact with a eukaryotic homolog of GroEL co-translationally, thereby sequestering the unfolded protein from other proteins in the cell. To test whether it is essential for GroEL to form a stable interaction with a nascent polypeptide co-translationally, we translated the well studied GroEL substrate rhodanese in bacterial and wheat germ translation extracts. We found that rhodanese formed stable complexes with GroEL solely posttranslationally. Upon binding to GroEL, the protease resistant N-terminal domain of rhodanese unfolds. This interaction with GroEL leads to productive folding of the full-length rhodanese. We conclude that GroEL is able to assist in the folding of newly synthesized proteins following release from the ribosome and that GroEL can unfold a trapped protein folding intermediate of rhodanese.
大肠杆菌伴侣蛋白GroEL是一类分子伴侣的成员，其具有堆叠的双环结构，每个环包含七个亚基，亚基分子量约为60 kDa。有人提出，新合成的蛋白质可能在共翻译过程中与GroEL的真核同源物相互作用，从而将未折叠的蛋白质与细胞中的其他蛋白质隔离开来。为了测试GroEL在共翻译过程中与新生多肽形成稳定相互作用是否必不可少，我们在细菌和小麦胚芽翻译提取物中翻译了研究充分的GroEL底物硫氧还蛋白。我们发现，硫氧还蛋白仅在翻译后与GroEL形成稳定的复合物。与GroEL结合后，硫氧还蛋白的蛋白酶抗性N端结构域会展开。与GroEL的这种相互作用导致全长硫氧还蛋白的有效折叠。我们得出结论，GroEL能够在从核糖体释放后协助新合成蛋白质的折叠，并且GroEL可以展开硫氧还蛋白被困的蛋白质折叠中间体。
