Structural insights into substrate binding to the ABC transport complex TAP

• Applicant: Privatdozent Dr. Rupert Abele
• Subject Area: Biochemistry
• Term: from 2007 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 45749231

The transporter associated with antigen processing (TAP) is a key element in the adaptive immune system. TAP recognizes and translocates cytosolic peptides into the ER lumen, where they are loaded onto major histocompatibility complex (MHC) class I molecules. TAP belongs to the family of ABC transporters, which translocate a large variety of solutes across membranes under consumption of ATP. Each subunit of the heterodimeric TAP complex comprises a transmembrane domain (TMD), which aligns the peptide-binding site and the translocation pathway, followed by a nucleotide-binding domain (NBD), which energizes the vectorial movement of peptides across the ER membrane. In previous studies, we have resolved the substrate specificity, the peptide-binding mechanism, and the coupling between peptide binding and ATP hydrolysis. We additionally studied the functional asymmetry of the subunits and identified a peptide contact region involved in quality control and signal transmission. However, crucial questions regarding the transport mechanism of TAP and ABC transporters in general remain unresolved. Within this project, we aim at understanding the ATP hydrolysis cycle and in particular it’s coupling to the peptide translocation cycle. We will examine the inter-domain crosstalk and conformational dynamics of the TAP complex during peptide transport. We will further investigate the architecture of the peptide-binding site by biochemical and biophysical approaches and tackle the structure of the TAP complex by 2D and 3D crystallization approaches.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Robert Tampé