How do ribosomes influence folding and misfolding of a multidomain protein during translation?

蛋白质在核糖体上以特定氨基酸序列的线性多肽链的形式合成。这种多肽融合了折叠成三维结构所需的所有信息，这是其功能所必需的，并且由于合成的矢量性质，可以在释放之前出现。错误折叠，即蛋白质被困在一个构象中，导致其功能不正常，也可能在仍在核糖体上时发生(Plessa等人。为了捕捉这种新生多肽的折叠过程，设计了核糖体-新生链状复合体(RNC)，并使用分泌监测器(SECM)停滞序列将其连接到核糖甲基肽转移酶中心(PTC)。通过这种方式，使用结构和生物化学方法观察到新生链(NCs)在与核糖体捆绑时采用类天然结构，具有长时间依赖的折叠开始。本项目旨在使用一种综合的方法来确定核糖体对延长的多肽施加什么控制，以鼓励多结构域复合体的顺序折叠，并另外防止未折叠的复合体采样错误折叠或容易聚集的构象。

Proteins are synthesized on the ribosome as linear polypeptide chains of a specific aminoacid sequence. This polypeptide incorporates all the information needed to fold into athree-dimensional structure which is integral to its function and, due to the vectoral natureof synthesis, can arise prior to release. Misfolding, where a protein becomes trapped in aconformation which causes it to misfunction, can also occur while still on the ribosome(Plessa et al. in prep), and can be implicated in human diseases including, but not limitedto, alpha-1 antitrypsin deficiency.To capture the process of folding this nascent polypeptide, ribosome-nascent chaincomplexes (RNCs) were designed with a protein paused and tethered to the ribosomepeptidyl transferase centre (PTC) using a secretion monitor (secM) stalling sequence. Inthis way, nascent chains (NCs) have been observed, using both structural and biochemicalmethods, to adopt native-like structures while tethered to ribosomes, with a lengthdependentonset of folding.This project aims to use an integrative approach to establish what control the ribosomeexerts on a lengthening polypeptide to encourage sequential folding of a multidomaincomplex and additionally prevent unfolded complexes from sampling misfolded oraggregation-prone conformations.