Interactions formed by individually expressed TAP1 and TAP2 polypeptide subunits.
The transporter associated with antigen processing (TAP) supplies peptides into the lumen of the endoplasmic reticulum (ER) for binding by major histocompatibility complex (MHC) class I molecules. TAP comprises two polypeptides, TAP1 and TAP2, each a 'half-transporter' encoding a transmembrane domain and a nucleotide-binding domain. Immunoprecipitation of rat TAP1 and TAP2 expressed individually in the human TAP-deficient cell line, T2, revealed that both bound the endogenously expressed HLA-A2 and -B51 class I molecules. Using HLA-encoding recombinant vaccinia viruses HLA-A*2501, -B*2704, -B*3501 and -B*4402, alleles also associated with both TAP1 and TAP2. Thus, TAP1 and TAP2 do not appear to differ in their ability to interact with MHC class I alleles. Single TAP polypeptide subunits also formed MHC class I peptide-loading complexes, and their nucleotide-binding domains retained the ability to interact with ATP, and may permit the release of peptide-loaded MHC class I molecules in the absence of a peptide transport cycle. It is also demonstrated by chemical cross-linking that TAP2, but not TAP1, has the ability to form a homodimer complex both in whole cells and in detergent lysates. Together these data indicate that single TAP polypeptide subunits possess many of the features of the TAP heterodimer, demonstrating them to be useful models in the study of ATP-binding cassette (ABC) transporters.
Antoniou
Antony N
AN
Division of Cell Biology and Immunology, School of Life Sciences, University of Dundee, Dundee, UK.
Ford
Stuart
S
Pilley
Elizabeth S
ES
Blake
Neil
N
Powis
Simon J
SJ
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D015789:HLA-A2 Antigen / Q000378:metabolism; D015235:HLA-B Antigens / Q000378:metabolism; D059949:HLA-B51 Antigen; D006801:Humans; D046911:Macromolecular Substances; D018832:Molecular Chaperones / Q000276:immunology; D051381:Rats; D014162:Transfection
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters; D015789:HLA-A2 Antigen; D015235:HLA-B Antigens; D059949:HLA-B51 Antigen; D046911:Macromolecular Substances; D018832:Molecular Chaperones; C073119:TAP1 protein, human; C486172:Tap1 protein, rat; C489514:Tap2 protein, rat; C071692:TAP2 protein, human; D000255:Adenosine Triphosphate