title: Membrane topology of the ATP-binding cassette transporter associated with antigen presentation (Tap1) expressed in Escherichia coli.
abstract: The ATP-binding cassette transporters associated with antigen presentation (Tap1 and Tap2) mediate the transport of peptide fragments across the endoplasmic reticulum membrane of mammalian cells. Tap1 and Tap2 are closely related to one another and are believed to function as a heterodimer. Each protein possesses a hydrophobic domain predicted to span the membrane multiple times and a highly conserved nucleotide-binding domain. We have assessed the transmembrane topology of Tap1 by expressing a series of fusions to a reporter protein, the mature form of beta-lactamase in Escherichia coli. From these data a topological model can be derived in which Tap1 spans the membrane eight times, with several large loops exposed in the lumen of the endoplasmic reticulum and with both the N and C termini (including the nucelotide-binding domain) residing in the cytoplasm.
authors.affiliation: Nuffield Department of Clinical Biochemistry and Imperial Cancer Research Fund Laboratories, Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
authors.forename: U
authors.initials: U
authors.lastname: Gileadi
authors.forename: C F
authors.initials: CF
authors.lastname: Higgins
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics; D000595:Amino Acid Sequence; D017951:Antigen Presentation; D002352:Carrier Proteins / Q000737:chemistry; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D017930:Genes, Reporter; D006801:Humans; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D011993:Recombinant Fusion Proteins; C073119:TAP1 protein, human; C461599:maltose transport system, E coli; C071692:TAP2 protein, human; D001618:beta-Lactamases