Modulation of ATP and drug binding by monoclonal antibodies against P-glycoprotein.
The role of P-glycoprotein in mediating the drug-resistance phenotype in multidrug resistant cells is now well documented. It is thought to function as an energy-dependent drug-efflux pump of broad specificity. Structurally, P-glycoprotein is an internally duplicated molecule containing two large multi-spanning transmembrane domains and two cytoplasmic ATP binding domains. In this report we demonstrate that monoclonal antibodies C219, C494, and C32 directed against short linear regions of the P-glycoprotein molecule inhibit ATP binding to P-glycoprotein in vitro. We also provide direct evidence that both predicted ATP-binding domains bind ATP and that there is co-operativity between the two sites. In addition, the capacity of P-glycoprotein to bind the calcium channel blocker, azidopine, is inhibited differentially by the antibodies. These observations are the first evidence linking specific perturbations of the P-glycoprotein molecule with ATP and drug binding.
Ontario Cancer Institute, Toronto, Canada.
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Georges
J T
JT
Zhang
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V
Ling
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism*; D000345:Affinity Labels / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001386:Azides / Q000378:metabolism*; D001665:Binding Sites; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D004095:Dihydropyridines / Q000378:metabolism*; D004351:Drug Resistance / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008961:Models, Structural; D008969:Molecular Sequence Data; D011487:Protein Conformation
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000345:Affinity Labels; D000911:Antibodies, Monoclonal; D001386:Azides; D004095:Dihydropyridines; D008562:Membrane Glycoproteins; C017040:8-azidoadenosine 5'-triphosphate; C041130:azidopine; D000255:Adenosine Triphosphate