title: Topological rules for membrane protein assembly in eukaryotic cells.
abstract: Insertion into the endoplasmic reticulum membrane of model proteins with one, two, and four transmembrane segments and different distributions of positively charged residues in the N-terminal tail and the polar loops has been studied both in vitro and in vivo. Membrane insertion of these same constructs has previously been analyzed in Escherichia coli, thus making possible a detailed comparison between the topological rules for membrane protein assembly in prokaryotic and eukaryotic cells. In general, we find that positively charged residues have similar effects on the membrane topology in both systems when they are placed in the N-terminal tail but that the effects of charged residues in internal loops clearly differ. Our results rule out a sequential start-stop transfer model where successive hydrophobic segments insert with alternating orientations starting from the most N-terminal one as the only mechanism for membrane protein insertion in eukaryotic cells.
authors.affiliation: Department of Biochemistry, Stockholm University, S-106 91 Stockholm, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Gafvelin
authors.forename: M
authors.initials: M
authors.lastname: Sakaguchi
authors.forename: H
authors.initials: H
authors.lastname: Andersson
authors.forename: G
authors.initials: G
authors.lastname: von Heijne
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000648:ultrastructure*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017510:Protein Folding; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D006023:Glycoproteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D012697:Serine Endopeptidases; C026515:type I signal peptidase