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。这种多肽包含了折叠成三维结构所需的所有信息，这是其功能的组成部分，并且由于合成的矢量性质，可以在释放之前产生。错误折叠，即蛋白质被困在构象中导致其功能失调，也可能发生在核糖体上（Plessa等人），并且可能与人类疾病有关，包括但不限于α -1抗胰蛋白酶缺乏症。为了捕捉这种新生多肽的折叠过程，我们设计了核糖体-新生链复合物（rna），其中一个蛋白质暂停，并使用分泌监视器（secM）延迟序列将其连接到核糖体肽基转移酶中心（PTC）。通过这种方式，使用结构和生化方法观察到新生链（NCs）在与核糖体连接时采用天然结构，具有长度依赖的折叠开始。该项目旨在使用一种综合方法来确定核糖体对延长多肽的控制，以促进多结构域复合物的顺序折叠，并防止未折叠的复合物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.