title: The ABC-transporter signature motif is required for peptide translocation but not peptide binding by TAP.
abstract: The transporter associated with antigen processing (TAP) translocates peptides from their site of generation in the cytosol to the lumen of the endoplasmic reticulum for binding to MHC class I molecules. TAP is a member of the ATP-binding cassette (ABC) transporter family whose members utilize energy from ATP hydrolysis to translocate substrates across membranes. The highly conserved nucleotide-binding domains of ABC transporters couple ATP hydrolysis to substrate translocation by the membrane domains. The conserved 'signature motif' can be identified in the nucleotide-binding domains of all ABC transporters, and may play a role in ATP hydrolysis. Here we show that introduction of mutations into the signature motifs of either TAP1 or TAP2 inhibits the translocation of peptide without affecting binding of either peptide or ATP by TAP. We therefore conclude that the signature motifs in both TAP1 and TAP2 are required after peptide binding to facilitate peptide translocation by TAP.
authors.affiliation: Division of Immunology, Department of Pathology, Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, GB. e.w.hewitt@leeds.ac.uk
authors.forename: Eric W
authors.initials: EW
authors.lastname: Hewitt
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Lehner
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 / Q000276:immunology; D000255:Adenosine Triphosphate / Q000378:metabolism; D020816:Amino Acid Motifs; D001665:Binding Sites; D002460:Cell Line; D016384:Consensus Sequence; D019281:Dimerization; D006801:Humans; D006868:Hydrolysis; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000276:immunology* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000502:physiology; D013329:Structure-Activity Relationship; D014162:Transfection
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; D010455:Peptides; D011993:Recombinant Fusion Proteins; C073119:TAP1 protein, human; C071692:TAP2 protein, human; D000255:Adenosine Triphosphate