Bernabeu C, Lake J A
Proc Natl Acad Sci U S A. 1982 May;79(10):3111-5. doi: 10.1073/pnas.79.10.3111.
The site of the nascent polypeptide chain as it leaves the ribosome has been localized on the "exit domain" of the Escherichia coli ribosome by using IgG antibodies directed against the enzyme beta-galactosidase (EC 3.2.1.23). Thus, a functional site has been mapped on intact 70S ribosomes. The exit site is on the large subunit, approximately 70 A from the interface between subunits and nearly 150 A from the central protuberance, the likely site of peptide transfer. It is adjacent to the region corresponding to the rough endoplasmic membrane binding region of the eukaryotic ribosome but distant from ribosomal components participating in mRNA recognition and polypeptide elongation (i.e., distant from the "translational domain"). These results, together with the protease protection experiments of others, provide evidence that the nascent protein chain probably passes through the ribosome in an unfolded, fully extended conformation.
利用针对β-半乳糖苷酶（EC 3.2.1.23）的IgG抗体，已将新生多肽链离开核糖体时的位点定位在大肠杆菌核糖体的“出口结构域”上。因此，一个功能位点已在完整的70S核糖体上得以定位。出口位点位于大亚基上，距离亚基间界面约70埃，距离可能的肽转移位点中央突起近150埃。它与真核核糖体粗糙内质网结合区域对应的区域相邻，但距离参与mRNA识别和多肽延伸的核糖体组分较远（即远离“翻译结构域”）。这些结果，连同其他人的蛋白酶保护实验，提供了证据表明新生蛋白质链可能以未折叠、完全伸展的构象穿过核糖体。
