Identification of Ligand-Binding Regions of P-Glycoprotein by Activated-Pharmacophore Photoaffinity Labeling and Matrix-Assisted Laser Desorption/Ionization–Time-of-Flight Mass Spectrometry
作者:Gerhard F. Ecker、Edina Csaszar、Stephan Kopp、Brigitte Plagens、Wolfgang Holzer、Wolfgang Ernst、Peter Chiba
DOI:10.1124/mol.61.3.637
日期:2002.3.1
Energy dependent efflux pumps confer resistance to anticancer, antimicrobial, and antiparasitic drugs. P-glycoprotein (Pgp, ABCB1) mediates resistance to a broad spectrum of antitumor drugs. Compounds that themselves are nontoxic to cells have been shown to act as inhibitors of Pgp. The mechanism of binding and transport of low-molecular-mass ligands by Pgp is still incompletely understood. This study introduces a series of propafenone-related photoaffinity ligands, which combine high specificity and selectivity for Pgp with high labeling efficiency. Molecules are intrinsically photoactivatable in the arylcarbonyl group, which represents a pharmacophoric substructure for this group of ligand molecules. A detailed study of the structure-activity relationship for this type of photoligand is presented. In subsequent experiments, these ligands were used to characterize the drug-binding domain of propafenone-type analogs. Matrix-assisted laser desorption/ionization—time-of-flight (MALDI-TOF) mass spectrometry shows that propafenone-type ligands preferentially label fragments assigned to putative transmembrane segments 3, 5, 6, 8, 10, 11, and 12. Labeled fragments are also identified in a highly charged region of 15 amino acids in the second cytoplasmic loop. This region corresponds to the so-called EAA-like motif, which has been proposed to play a role in the interaction between transmembrane domain and nucleotide binding domain of peroxisomal ATP-binding cassette transporters. In addition, a region in cytoplasmic loop 3 and between TM12 and the N terminus of the Walker A sequence of NBD2 are labeled by the ligands. Therefore, a number of confined protein regions contribute to the drug-binding domain of propafenone-type analogs.
依赖能量的排出泵使抗癌药、抗微生物药和抗寄生虫药产生耐药性。P-糖蛋白(Pgp,ABCB1)介导对广谱抗肿瘤药物的耐药性。已证明某些对细胞本身无毒的化合物可以作为Pgp的抑制剂。Pgp对低分子量配体的结合和转运机制仍未完全了解。本研究介绍了一系列与普罗帕酮相关的光亲和配体,这些配体对Pgp具有高特异性和选择性,并且标记效率高。这些分子在芳基羰基基团中具有内在的光激活性,该基团代表了这类配体分子的药效团子结构。本文详细研究了这类光配体的结构-活性关系。在后续实验中,这些配体被用于表征普罗帕酮类类似物的药物结合区域。基质辅助激光解吸/电离-飞行时间(MALDI-TOF)质谱显示,普罗帕酮类配体优先标记分配给假定跨膜片段3、5、6、8、10、11和12的片段。标记片段也在第二个胞质环的15个氨基酸的高电荷区域中被鉴定出来。该区域对应所谓的EAA样基序,据信在过氧化物酶体ATP结合盒转运蛋白的跨膜域与核苷酸结合域之间的相互作用中发挥作用。此外,配体还标记胞质环3中的一个区域,以及跨膜12(TM12)与NBD2的沃克A序列N末端之间的区域。因此,一些特定的蛋白区域共同参与普罗帕酮类类似物的药物结合域。