title: Cotranslational folding of membrane proteins probed by arrest-peptide-mediated force measurements.
abstract: Polytopic membrane proteins are inserted cotranslationally into target membranes by ribosome-translocon complexes. It is, however, unclear when during the insertion process specific interactions between the transmembrane helices start to form. Here, we use a recently developed in vivo technique to measure pulling forces acting on transmembrane helices during their cotranslational insertion into the inner membrane of Escherichia coli to study the earliest steps of tertiary folding of five polytopic membrane proteins. We find that interactions between residues in a C-terminally located transmembrane helix and in more N-terminally located helices can be detected already at the point when the C-terminal helix partitions from the translocon into the membrane. Our findings pinpoint the earliest steps of tertiary structure formation and open up possibilities to study the cotranslational folding of polytopic membrane proteins.
authors: Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
authors: Florian
authors: F
authors: Cymer
authors: Gunnar
authors: G
authors: von Heijne
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017920:Antiporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D014176:Protein Biosynthesis; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012270:Ribosomes / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D017920:Antiporters; C050021:BtuC peptide, E coli; C469350:CaiT protein, E coli; C510268:EmrD protein, E coli; D029968:Escherichia coli Proteins; C488962:GlpT protein, E coli; D026901:Membrane Transport Proteins; C102839:NhaA protein, E coli; D017923:Sodium-Hydrogen Exchangers
keywords: helix-helix interactions; membrane insertion; protein folding
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