Wiedmann B, Sakai H, Davis T A, Wiedmann M
Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Nature. 1994 Aug 11;370(6489):434-40. doi: 10.1038/370434a0.
We have purified a nascent-polypeptide-associated complex (NAC) which prevents short ribosome-associated nascent polypeptides from inappropriate interactions with proteins in the cytosol. NAC binds nascent-polypeptide domains emerging from ribosomes unless a signal peptide is fully exposed. Depletion of cytosolic proteins (including NAC) from ribosomes carrying nascent polypeptides allows the signal recognition particle (SRP) to crosslink to polypeptides irrespective of whether or not they contain signal peptides. In the absence of cytosol, proteins lacking signal peptides can be mistranslocated into the endoplasmic reticulum in vitro, albeit with low efficiency. Readdition of NAC restores the specificity of SRP and fidelity of translocation.
我们纯化了一种新生多肽相关复合物（NAC），它可防止与核糖体相关的短新生多肽与胞质溶胶中的蛋白质发生不适当相互作用。除非信号肽完全暴露，NAC会结合从核糖体中出现的新生多肽结构域。从携带新生多肽的核糖体中去除胞质溶胶蛋白（包括NAC）后，信号识别颗粒（SRP）能够与多肽交联，无论这些多肽是否含有信号肽。在没有胞质溶胶的情况下，缺乏信号肽的蛋白质在体外可错误转运到内质网中，尽管效率很低。重新添加NAC可恢复SRP的特异性和转运的保真度。
