Möller I, Beatrix B, Kreibich G, Sakai H, Lauring B, Wiedmann M
Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
FEBS Lett. 1998 Dec 11;441(1):1-5. doi: 10.1016/s0014-5793(98)01440-9.
Nascent polypeptide associated complex (NAC) interacts with nascent polypeptides emerging from ribosomes. Both signal recognition particle (SRP) and NAC work together to ensure specificity in co-translational targeting by competing for binding to the ribosomal membrane attachment site. While SRP selects signal-containing ribosomes for targeting, NAC prevents targeting of signal peptide-less nascent chains to the endoplasmic reticulum membrane. Here we show that the ribosome binding that occurs in NAC's absence delivers signalless nascent chains to the Sec61 complex, underscoring the danger of unregulated exposure of the ribosomal M-site. Recently, the idea that NAC prevents ribosome binding has been challenged. By carefully examining the physiologic NAC concentration in a variety of tissues from different species we here demonstrate that the discrepancy resulted from subphysiologic NAC concentrations.
新生多肽相关复合体（NAC）与从核糖体中出现的新生多肽相互作用。信号识别颗粒（SRP）和NAC共同作用，通过竞争结合核糖体膜附着位点来确保共翻译靶向的特异性。当SRP选择含信号的核糖体进行靶向时，NAC可防止无信号肽的新生链靶向内质网膜。我们在此表明，在没有NAC的情况下发生的核糖体结合会将无信号的新生链传递给Sec61复合体，这突出了核糖体M位点不受调控暴露的危险性。最近，NAC阻止核糖体结合这一观点受到了挑战。通过仔细检测来自不同物种的多种组织中的生理NAC浓度，我们在此证明这种差异是由亚生理浓度的NAC导致的。
