Partial purification and reconstitution of the human multidrug-resistance pump: characterization of the drug-stimulatable ATP hydrolysis.

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Ambudkar SV, Lelong IH, Zhang J, Cardarelli CO, Gottesman MM, Pastan I

Partial purification and reconstitution of the human multidrug-resistance pump: characterization of the drug-stimulatable ATP hydrolysis.

Proc Natl Acad Sci U S A. 1992 Sep 15;89(18):8472-6.

PubMed ID

1356264 [ View in PubMed

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Abstract

Multidrug-resistant human tumor cells overexpress the MDR1 gene product P-glycoprotein, which is believed to function as an ATP-dependent efflux pump. In this study we demonstrate that the partially purified P-glycoprotein, when reconstituted in an artificial membrane, catalyzes drug-stimulated ATP hydrolysis. Plasma membrane proteins of a human multidrug-resistant cell line, KB-V1, were solubilized with 1.4% (wt/vol) octyl beta-D-glucopyranoside in the presence of 0.4% phospholipid and 20% (vol/vol) glycerol, and the crude detergent extract was chromatographed on DEAE-Sepharose CL-6B. The 0.1 M NaCl fraction, enriched in P-glycoprotein but devoid of Na,K-ATPase, was reconstituted by the detergent-dilution method. P-glycoprotein constituted 25-30% of the reconstituted protein in proteoliposomes. ATP hydrolysis by proteoliposomes was stimulated 3.5-fold by the addition of vinblastine but was unaffected by the hydrophobic antitumor agent camptothecin, which is not transported by P-glycoprotein. The stimulatory effect of vinblastine was observed only if the protein was reconstituted in proteoliposomes, suggesting that either the substrate binding site(s) was masked by detergent or that the conformation of the soluble P-glycoprotein might not be suitable for substrate-induced activation. Several other drugs that are known to be transported by P-glycoprotein enhanced the ATPase activity in a dose-dependent manner with relative potencies as follows: doxorubicin = vinblastine greater than daunomycin greater than actinomycin D greater than verapamil greater than colchicine. The basal and vinblastine-stimulated ATPase activities were inhibited by vanadate (50% inhibition observed at 7-10 microM) but were not affected by agents that inhibit other ATPases and phosphatases. These data indicate that the P-glycoprotein, similar to other ion-transporting ATPases, exhibits a high level of ATP hydrolysis (5-12 mumol per min per mg of protein).

DrugBank Data that Cites this Article

Drug Transporters

Drug	Transporter	Kind	Organism	Pharmacological Action	Actions
Dactinomycin	P-glycoprotein 1	Protein	Humans	Unknown	Substrate Inhibitor	Details
Doxorubicin	P-glycoprotein 1	Protein	Humans	Unknown	Substrate Inhibitor Inducer	Details