Mechanism of substrate sensing and signal transmission within an ABC transporter: use of a Trojan horse strategy.
By translocating proteasomal degradation products into the endoplasmic reticulum for loading of major histocompatibility complex I molecules, the ABC transporter TAP plays a focal role in the adaptive immunity against infected or malignantly transformed cells. A key question regarding the transport mechanism is how the quality of the incoming peptide is detected and how this information is transmitted to the ATPase domains. To identify residues involved in this process, we evolved a Trojan horse strategy in which a small artificial protease is inserted into antigenic epitopes. After binding, the TAP backbone in contact is cleaved, allowing the peptide sensor site to be mapped by mass spectrometry. Within this sensor site, we identified residues that are essential for tight coupling of peptide binding and transport. This sensor and transmission interface is restructured during the ATP hydrolysis cycle, emphasizing its important function in the cross-talk between the transmembrane and the nucleotide-binding domains. This allocrite sensor may be similarly positioned in other members of the ABC exporter family.
Herget
Meike
M
Institute of Biochemistry, Biocenter, Goethe-University Frankfurt, Max-von-Laue-Strasse 9, D-60438 Frankfurt am Main, Germany.
Oancea
Giani
G
Schrodt
Susanne
S
Karas
Michael
M
Tampé
Robert
R
Abele
Rupert
R
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D017951:Antigen Presentation / Q000235:genetics; D015395:Histocompatibility Antigens Class I / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D013379:Substrate Specificity / Q000235:genetics
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D010446:Peptide Fragments; C073119:TAP1 protein, human