title: Stop-transfer efficiency of marginally hydrophobic segments depends on the length of the carboxy-terminal tail.
abstract: Hydrophobic stop-transfer sequences generally serve to halt the translocation of polypeptide chains across the endoplasmic reticulum membrane and become integrated as transmembrane alpha-helices. Using engineered glycosylation sites as topology reporters, we show that the length of the nascent chain between a hydrophobic segment and the carboxy terminus of the protein can affect stop-transfer efficiency. We also show that glycosylation sites located close to a protein's C terminus are modified in two distinct kinetic phases, one fast and one slow. Our findings suggest that membrane integration of a hydrophobic segment is not simply a question of thermodynamic equilibrium, but can be influenced by details of the translocation mechanism.
authors.affiliation: Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
authors.forename: Tara
authors.initials: T
authors.lastname: Hessa
authors.forename: Magnus
authors.initials: M
authors.lastname: Monné
authors.forename: Gunnar
authors.initials: G
authors.lastname: von Heijne
mesh_terms: D006031:Glycosylation; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D010455:Peptides / Q000378:metabolism; D021382:Protein Sorting Signals / Q000502:physiology*
chemical_list: D010455:Peptides; D021382:Protein Sorting Signals; C027819:polyleucine