ATP‐binding properties of P glycoprotein from multidrug‐resistant KB cells

The photoaffinity reagent 8‐azido‐α‐[ 32 P]ATP was used to label a protein of 170 kDa in membrane vesicle preparations from a highly multidrug‐resistant cell line, KB‐V1, but not from the drug‐sensitive parental cell line KB‐3‐1. The 170‐kDa labeled protein was immunoprecipitated with a monoclonal antibody (MRK‐16) to P glycoprotein. Both ATP and GTP inhibited labeling by 8‐azido‐α‐[ 52 P]ATP. Labeling of P170 was not inhibited by 5 mM ADP, 5 m m ribose‐5‐phosphate, or 100 μ m vinblastine. These data directly demonstrate that P glycoprotein has a nucleotide‐binding site that could supply energy for drug transport.— C ornwell , M. M.; T suruo , T; G ottesman , M. M.; P astan , I. ATP‐binding properties of P glycoprotein from multidrug‐resistant KB cells. FASEB J 1: 51‐54; 1987.