A Nascent Secretory Protein 5 Traverse the Ribosome/Endoplasmic Reticulum Translocase Complex as an Extended Chain

We have measured the minimum number of residues in a translocating polypeptide required to bridge the distance between the P-site in endoplasmic reticulum-bound ribosomes and the lumenally disposed active site of the oligosaccharyl transferase. The results suggest that a nascent chain may traverse the ribosome/translocase complex in a largely extended conformation, and that hydrophobic stop-transfer segments have a more compact, possibly α-helical conformation in the translocase. We have measured the minimum number of residues in a translocating polypeptide required to bridge the distance between the P-site in endoplasmic reticulum-bound ribosomes and the lumenally disposed active site of the oligosaccharyl transferase. The results suggest that a nascent chain may traverse the ribosome/translocase complex in a largely extended conformation, and that hydrophobic stop-transfer segments have a more compact, possibly α-helical conformation in the translocase.