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Preparation of Bead-supported Lipid Bilayers to Study the Particulate Output of T Cell Immune Synapses
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Specific lipids modulate the transporter associated with antigen processing (TAP)

Christian Schölz1, David Parcej, Christer S Ejsing

  • 1Institute of Biochemistry, Biocenter, Goethe-University Frankfurt, Max-von-Laue Strasse 9, D-60438 Frankfurt am Main, Germany.

The Journal of Biological Chemistry
|March 2, 2011
PubMed

The transporter associated with antigen processing (TAP) plays a key role in adaptive immunity by translocating proteasomal degradation products from the cytosol into the endoplasmic reticulum lumen for subsequent loading onto major histocompatibility (MHC) class I molecules. For functional and structural analysis of this ATP-binding cassette complex, we established the overexpression of TAP in the methylotrophic yeast Pichia pastoris. Screening of optimal solubilization and purification conditions allowed the isolation of the heterodimeric transport complex, yielding 30 mg of TAP/liter of culture. Detailed analysis of TAP function in the membrane, solubilized, purified, and reconstituted states revealed a direct influence of the native lipid environment on activity. TAP-associated phospholipids, essential for function, were profiled by liquid chromatography Fourier transform mass spectrometry. The antigen translocation activity is stimulated by phosphatidylinositol and -ethanolamine, whereas cholesterol has a negative effect on TAP activity.

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