title: A dual inhibition mechanism of herpesviral ICP47 arresting a conformationally thermostable TAP complex.
abstract: As a centerpiece of antigen processing, the ATP-binding cassette transporter associated with antigen processing (TAP) became a main target for viral immune evasion. The herpesviral ICP47 inhibits TAP function, thereby suppressing an adaptive immune response. Here, we report on a thermostable ICP47-TAP complex, generated by fusion of different ICP47 fragments. These fusion complexes allowed us to determine the direction and positioning in the central cavity of TAP. ICP47-TAP fusion complexes are arrested in a stable conformation, as demonstrated by MHC I surface expression, melting temperature, and the mutual exclusion of herpesviral TAP inhibitors. We unveiled a conserved region next to the active domain of ICP47 as essential for the complete stabilization of the TAP complex. Binding of the active domain of ICP47 arrests TAP in an open inward facing conformation rendering the complex inaccessible for other viral factors. Based on our findings, we propose a dual interaction mechanism for ICP47. A per se destabilizing active domain inhibits the function of TAP, whereas a conserved C-terminal region additionally stabilizes the transporter. These new insights into the ICP47 inhibition mechanism can be applied for future structural analyses of the TAP complex.
authors.affiliation: Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt a.M., Germany.
authors.forename: Valentina
authors.initials: V
authors.lastname: Herbring
authors.affiliation: Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt a.M., Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Bäucker
authors.affiliation: Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt a.M., Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Trowitzsch
authors.affiliation: Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt a.M., Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Tampé
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2 / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D017951:Antigen Presentation / Q000502:physiology*; D002460:Cell Line; D057809:HEK293 Cells; D015395:Histocompatibility Antigens Class I / Q000378:metabolism; D006801:Humans; D017874:Immediate-Early Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D055550:Protein Stability; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D016415:Sequence Alignment; D018139:Simplexvirus / Q000378:metabolism*; D013696:Temperature
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D015395:Histocompatibility Antigens Class I; C105843:ICP47 protein, Herpes simplex virus; D017874:Immediate-Early Proteins; D011993:Recombinant Fusion Proteins