Protein folding during cotranslational translocation in the endoplasmic reticulum.
To test how far into the protein-conducting channel of the translocon complex a nascent polypeptide domain must move before it can fold, we analyzed the folding of in vitro translated products of truncated mRNAs encoding the Semliki Forest virus capsid protease domain (Cp) during translocation into microsomes. Cp folded when the C-terminal linker connecting it to the peptidyltransferase center was 64 amino acids or longer. This means that to fold, Cp must exit the translocon channel. With an uncleaved signal sequence, about one out of four of the Cp domains could undergo folding with a C-terminal linker of only 38-66 amino acids. This suggested that the constraint imposed on folding by the translocon complex may be less stringent for signal-anchored membrane proteins.
Kowarik
Michael
M
Institute of Biochemistry, Swiss Federal Institute of Technology, ETH Hönggerberg, HPM, CH-8093, Zürich, Switzerland.
Küng
Stephanie
S
Martoglio
Bruno
B
Helenius
Ari
A
D000595:Amino Acid Sequence; D001665:Binding Sites; D036022:Capsid Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D017930:Genes, Reporter; D007425:Intracellular Membranes / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D010458:Peptidyl Transferases / Q000737:chemistry / Q000378:metabolism; D014176:Protein Biosynthesis; D017510:Protein Folding; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism; D012672:Semliki forest virus
D036022:Capsid Proteins; D021382:Protein Sorting Signals; D012333:RNA, Messenger; D010458:Peptidyl Transferases