FUNCTIONAL EXPRESSION AND PURIFICATION OF THE ABC TRANSPORTER COMPLEX-ASSOCIATED WITH ANTIGEN-PROCESSING (TAP) IN INSECT CELLS

Using the baculovirus expression system the gene products of human tap 1 and tap2 were over-expressed as wild-type as well as oligohistidine fusion proteins in Spodoptera frugiperda (Sf9) insect cells. Both gene products were co-expressed within the same cells and were found enric hed in microsomal membranes. Immunoprecipitation and immobilized metal affinity chromatography revealed complex formation between TAP1 and T AP2. The expressed TAP complex was shown to be functional by peptide t ranslocation into microsomes of Sf9 cells. Peptide transport strictly requires TAP1 and TAP2 as well as ATP. For the first time the function al expression of the human TAP complex in insect cells has been demons trated, indicating that additional cofactors of a highly developed imm une system are not essential for peptide transport across microsomal m embranes.