P-glycoprotein detoxifies cells by exporting hundreds of chemically dissimilar hydrophobic and amphipathic compounds and is implicated in multidrug resistance (MDR) in the treatment of cancers. Photoaffinity labelling of plasma membrane vesicles of MDR CHO B30 cells with the anthracycline [(125) I]-iodomycin, subsequent sequential cleavage with BNPS-skatol and endoproteinase LysC and Edman sequencing of the purified photoaffinity-labelled peptide identified the lysine residue at position 268 in the hamster P-glycoprotein primary sequence as the major photobinding site of iodomycin in CHO B30 cells. Lysine 268 is located adjacent to the cytosolic terminus of transmembrane 5. According to thermodynamic and kinetic analyses, this location should present the equilibrium binding site of ATP-free P-glycoprotein for daunomycin and iodomycin in B30 cells.
- Demmer, A.
- Thole, H.
- Raida, M.
- Tümmler, B.
Keywords
- ABC transporter
- Edman sequencing
- P-glycoprotein
- anthracycline
- drug binding site
- multidrug-resistance
