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[摘要]：P-glycoprotein (ABCB1) is an ATP-driven efflux pump which binds drugs within a large flexible binding pocket. Intrinsic Trp fluorescence was used to probe the interactions of LDS-751 (2-[4-(4-[dimethylamino]phenyl)-1,3-butadienyl]-3-ethylbenzo-thiazolium perchlorate) with purified P-glycoprotein, using steady-state/lifetime measurements and collisional quenching. The fast decay component of P-glycoprotein intrinsic fluorescence (tau(1) = 0.97 ns) was unaffected by LDS-751 binding, while the slow decay component (tau(2) = 4.02 ns) was quenched by dynamic and static mechanisms. Both the wavelength-dependence of the decay kinetics, and the time-resolved emission spectra, suggested the existence of excited-state relaxation processes within the protein matrix on the nanosecond time-scale, which were altered by LDS-751 binding. The fast decay component, which is more solvent-exposed, can be attributed to cytosolic/extracellular Trp residues, while the slow decay component likely arises from more buried transmembrane Trp residues. Interaction Of a drug With the binding pocket of P-glycoprotein thus affects its molecular structure and fast dynamics. (C) 2009 Elsevier Inc. All rights reserved. |
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