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Updated: Aug 29, 2026

Affinity Purification of Chloroplast Translocon Protein Complexes Using the TAP Tag
07:01

Affinity Purification of Chloroplast Translocon Protein Complexes Using the TAP Tag

Published on: November 1, 2018

Functional dissection of the transmembrane domains of the transporter associated with antigen processing (TAP)

Joachim Koch1, Renate Guntrum, Susanne Heintke

  • 1Institute of Biochemistry, Biocenter, Johann Wolfgang Goethe-University Frankfurt, Germany.

The Journal of Biological Chemistry
|December 18, 2003
PubMed

The transporter associated with antigen processing (TAP1/2) translocates cytosolic peptides of proteasomal degradation into the endoplasmic reticulum (ER) lumen. A peptide-loading complex of tapasin, major histocompatibility complex class I, and several auxiliary factors is assembled at the transporter to optimize antigen display to cytotoxic T-lymphocytes at the cell surface. The heterodimeric TAP complex has unique N-terminal domains in addition to a 6 + 6-transmembrane segment core common to most ABC transporters. Here we provide direct evidence that this core TAP complex is sufficient for (i) ER targeting, (ii) heterodimeric assembly within the ER membrane, (iii) peptide binding, (iv) peptide transport, and (v) specific inhibition by the herpes simplex virus protein ICP47 and the human cytomegalovirus protein US6. We show for the first time that the translocation pore of the transporter is composed of the predicted TM-(5-10) of TAP1 and TM-(4-9) of TAP2. Moreover, we demonstrate that the N-terminal domains of TAP1 and TAP2 are essential for recruitment of tapasin, consequently mediating assembly of the macromolecular peptide-loading complex.

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