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

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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.