| First Author | Urbatsch IL | Year | 2003 |
| Journal | J Biol Chem | Volume | 278 |
| Issue | 25 | Pages | 23171-9 |
| PubMed ID | 12670938 | Mgi Jnum | J:84118 |
| Mgi Id | MGI:2665236 | Doi | 10.1074/jbc.M301957200 |
| Citation | Urbatsch IL, et al. (2003) P-glycoprotein catalytic mechanism: studies of the ADP-vanadate inhibited state. J Biol Chem 278(25):23171-9 |
| abstractText | Kinetics of inhibition of ATPase activity of pure mouse Mdr3 P-glycoprotein upon incubation with MgADP and vanadate were studied along with the trapping of [14C]ADP in presence of vanadate. The presence of verapamil strongly magnified both effects. Inhibition of ATPase was also increased by several other drugs known to bind to drug-binding sites. Inhibition by ADP-vanadate was slow and depended cooperatively on nucleotide binding. Stoichiometry of [14C]ADP trapping by vanadate was 1 mol/mol P-glycoprotein at full inhibition. Catalytic site mutants prevented [14C]ADP trapping, whereas interdomain signal communication mutants reduced it in approximate correlation with their effects upon drug stimulation of ATPase. In explanation of the results, we propose that a 'closed conformation' involving dimerization and interdigitation of the two nucleotide-binding domains is necessary to allow inhibition by ADP-vanadate. The results suggest that such a conformation occurs naturally during ATP hydrolysis. It is proposed that in order for the catalytic transition state to form, the two nucleotide-binding domains dimerize to form an integrated single entity containing two bound ATP with just one of the two ATP being hydrolyzed per dimerization event. |
