Quantification and Characterization of P-Glycoprotein-Substrate Interactions
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- 作者：Ewa Gatlik-Landwojtowicz ; Pä ; ivi Ä ; ä ; nismaa ; and Anna Seelig
- 刊名：Biochemistry
- 出版年：2006
- 出版时间：March 7, 2006
- 年：2006
- 卷：45
- 期：9
- 页码：3020 - 3032
- 全文大小：245K
- 年卷期：v.45,no.9(March 7, 2006)
- ISSN：1520-4995
文摘
It is generally accepted that P-glycoprotein binds its substrates in the lipid phase of themembrane. Quantification and characterization of the lipid-transporter binding step are, however, still amatter of debate. We therefore selected 15 structurally diverse drugs and measured the binding constantsfrom water to the activating (inhibitory) binding region of P-glycoprotein, Ktw(1) (Ktw(2)), as well as thelipid-water partition coefficients, Klw. The former were obtained by measuring the concentrations ofhalf-maximum activation (inhibition), K1 (K2), in living NIH-MDR-G185 mouse embryo fibroblasts usinga Cytosensor microphysiometer, and the latter were derived from surface activity measurements. Thisallowed determination of the membrane concentration of drugs at half-maximum P-glycoprotein activation(Cb(1) = (0.02 to 67) mmol/L lipid), which is much higher than the corresponding aqueous concentration(K1 = (0.02 to 376) 
M). Moreover we determined the free energy of drug binding from water to theactivating binding region of the transporter (
G
tw(1) = (-30 to -54) kJ/mol), the free energy of drugpartitioning into the lipid membrane (Glw = (-23 to -34) kJ/mol), and, as the difference of the two,the free energy of drug binding from the lipid membrane to the activating binding region of the transporter(Gtl(1) = (-7 to -27) kJ/mol). For the compounds tested Gtl(1) was less negative than Glw butvaried more strongly. The free energies of substrate binding to the transporter within the lipid phase,Gtl(1), are consistent with a modular binding concept, where the energetically most efficient bindingmodule comprises two hydrogen bond acceptor groups.
M). Moreover we determined the free energy of drug binding from water to theactivating binding region of the transporter (Gtw(1) = (-30 to -54) kJ/mol), the free energy of drugpartitioning into the lipid membrane (Glw = (-23 to -34) kJ/mol), and, as the difference of the two,the free energy of drug binding from the lipid membrane to the activating binding region of the transporter(Gtl(1) = (-7 to -27) kJ/mol). For the compounds tested Gtl(1) was less negative than Glw butvaried more strongly. The free energies of substrate binding to the transporter within the lipid phase,Gtl(1), are consistent with a modular binding concept, where the energetically most efficient bindingmodule comprises two hydrogen bond acceptor groups.