Epstein-Barr viral protein BNLF2a suppresses the conformational change of antigenic peptide transporter TAP

Abstract:

[Background] Epstein-Barr virus (EBV) is a common pathogen causing Burkitt’s lymphoma, Hodgkin’s disease, gastric cancer and nasopharyngeal carcinoma. A membrane protein BNLF2a encoded by EBV inhibits antigen transportation by transporter associated with antigen processing (TAP) and thereby evades the elimination by cytotoxic T cells. TAP is a member of the ATP-binding cassette (ABC) superfamily and composed of two subunits of TAP1 and TAP2. Using the energy of ATP hydrolysis, TAP transports antigenic peptides across the membrane with a conformational change. [Objective] The aim of this study was to study if BNLF2a affects the conformational switch of TAP. [Methods] Cysteines were introduced into the D-loop at the interface of TAP’s nucleotide binding domains. TAP were cross-linked by oxidizing agent Cu(II). The ratios of disulfide formed TAP were compared in the presence or absence of BNLF2a by western blot. [Results] The expression of BNLF2a increased the ratio of cross-linked TAP. [Conclusion] BNLF2a appears to stabilize TAP in the nucleotide binding domains dimerized conformation and thereby inhibit both of ATP and antigenic peptide binding to TAP.