title: Three-dimensional structure of transporter associated with antigen processing (TAP) obtained by single Particle image analysis.
abstract: The transporter associated with antigen processing (TAP) is an ATP binding cassette transporter responsible for peptide translocation into the lumen of the endoplasmic reticulum for assembly with major histocompatibility complex class I molecules. Immunoaffinity-purified TAP particles comprising TAP1 and TAP2 polypeptides, and TAP2 particles alone were characterized after detergent solubilization and studied by electron microscopy. Projection structures of TAP1+2 particles reveal a molecule approximately 10 nm across with a deeply staining central region, whereas TAP2 molecules are smaller in projection. A three-dimensional structure of TAP reveals it is isolated as a single heterodimeric complex, with the TAP1 and TAP2 subunits combining to create a central 3-nm-diameter pocket on the predicted endoplasmic reticulum-lumenal side. Its structural similarity to other ABC transporters demonstrates a common tertiary structure for this diverse family of membrane proteins.
authors.affiliation: Department of Biomolecular Sciences, UMIST, Manchester M60 1QD, United Kingdom.
authors.forename: G
authors.initials: G
authors.lastname: Velarde
authors.forename: R C
authors.initials: RC
authors.lastname: Ford
authors.forename: M F
authors.initials: MF
authors.lastname: Rosenberg
authors.forename: S J
authors.initials: SJ
authors.lastname: Powis
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000941:Antigens / Q000378:metabolism; D002460:Cell Line; D005434:Flow Cytometry; D011487:Protein Conformation; D051381:Rats
chemical_list: D018528:ATP-Binding Cassette Transporters; D000941:Antigens