title: Membrane protein spanning segments as export signals.
abstract: Escherichia coli lac permease is a polytopic integral membrane protein with six translocated (periplasmic) domains. Individual N-terminal cytoplasmic regions and membrane-spanning segments adjacent to each of the periplasmic domains acted as export signals for an attached sensor protein (alkaline phosphatase). However, the export activity of one of the spanning segments was considerably lower than that of the others, and was limited by the presence of a positively charged residue (Arg302). These observations are compatible with models of membrane protein insertion in which hydrophilic domains are translocated independently. However, the results suggest that efficient translocation may sometimes require interaction between individual spanning segments.
authors.affiliation: Department of Genetics, SK-50, University of Washington, Seattle 98195.
authors.forename: J
authors.initials: J
authors.lastname: Calamia
authors.forename: C
authors.initials: C
authors.lastname: Manoil
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics; D029968:Escherichia coli Proteins; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D011487:Protein Conformation; D027981:Symporters
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D027981:Symporters; C021499:lactose permease