title: Identification and evolution of dual-topology membrane proteins.
abstract: Integral membrane proteins are generally believed to have unique membrane topologies. However, it has been suggested that dual-topology proteins that adopt a mixture of two opposite orientations in the membrane may exist. Here we show that the membrane orientations of five dual-topology candidates identified in Escherichia coli are highly sensitive to changes in the distribution of positively charged residues, that genes in families containing dual-topology candidates occur in genomes either as pairs or as singletons and that gene pairs encode two oppositely oriented proteins whereas singletons encode dual-topology candidates. Our results provide strong support for the existence of dual-topology proteins and shed new light on the evolution of membrane-protein topology and structure.
authors.affiliation: Center for Biomembrane Research, Department of Biochemistry and Biophysics, AlbaNova, Stockholm University, SE-10691 Stockholm, Sweden.
authors.forename: Mikaela
authors.initials: M
authors.lastname: Rapp
authors.forename: Erik
authors.initials: E
authors.lastname: Granseth
authors.forename: Susanna
authors.initials: S
authors.lastname: Seppälä
authors.forename: Gunnar
authors.initials: G
authors.lastname: von Heijne
mesh_terms: D000595:Amino Acid Sequence; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins