Influence of substrate structure on substrate binding to the renal organic cation/H+ exchanger.
Influence of substrate structure on substrate binding to the renal organic cation/H+ exchanger.
复制标题
底物结构对底物与肾有机阳离子/H 交换剂结合的影响。
DOI：
10.1007/s004240050823
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Wunz,TM
中科院分区：
文献类型：
--
作者：
Wright,SH;Wunz,TM
载体介导的H+与有机阳离子的交换（“OC/H+交换”）是肾近端小管OC分泌的活跃步骤。虽然疏水性是已知的是一个重要的标准结合的基板，这种转运，在何种程度上的空间参数的基板结构的影响结合的交换器是不清楚的。我们研究了这个问题，通过测量抑制OC/H+交换产生的一组季铵化合物，其中有一个共同的结构基序：anN 1-吡啶残留物。OC/H+交换器的活性通过测量[14 C]四乙基铵（TEA）在兔肾皮质刷状缘膜囊泡（BBMV）中的转运来确定。在pH梯度（pHin 6.0; pHout 7.5）存在下测量转运以使TEA/H+交换最大化。测量每种测试试剂的表观抑制常数（Ki值）。测试试剂包括4-苯基吡啶鎓和3-苯基吡啶鎓、喹啉鎓和吖啶鎓。这些化合物的平面结构允许直接测试相对于吡啶基序的不同取向的平面疏水质量的存在是否对与OC/H+交换剂结合的底物产生系统性影响。各组化合物的疏水性通过在季氮上添加不同的取代基而系统地变化。尽管K1的降低被证明与疏水性成正比，但苯环取代基的位置对底物与交换剂的相互作用没有影响。结果导致了初步的定量结构活性关系（QSAR）的发展相关的基板疏水性和基板结合的OC/H+交换。用该构效关系预测了1-甲基-4-苯基吡啶（MPP+）、（+）和（-）尼古丁、（+）和（-）麻黄碱、奎宁和奎尼丁与OC/H+交换体的结合。测试剂的3D结构的分子图形表示用于开发OC/H+交换器上的疏水性平面受体表面的工作模型，建议底物在结合过程中相互作用。QSAR和受体表面模型的开发为定量测试肾脏OC/H+交换剂底物选择性的特定物理和结构决定因素开辟了道路。
The carrier-mediated exchange of H+for organic cations (”OC/H+exchange”) is the active step in OC secretion in renal proximal tubules. Although hydrophobicity is known to be an important criterion for binding of substrates to this transporter, the degree to which steric parameters of substrate structure influence binding to the exchanger is unclear. We examined this issue by measuring the inhibition of OC/H+exchange produced by a group of quaternary ammonium compounds which share a common structural motif: anN1-pyridinium residue. Activity of the OC/H+exchanger was determined by measuring transport of [14C]tetraethylammonium (TEA) in brush-border membrane vesicles (BBMV) from rabbit renal cortex. Transport was measured in the presence of a pH gradient (pHin6.0; pHout7.5) to maximize TEA/H+exchange. Apparent inhibitory constants (Kivalues) for each test agent were measured. The test agents included 4-phenylpyridiniums and 3-phenylpyridiniums, quinoliniums and acridiniums. The planar structure of these compounds permits a direct test of whether the presence of planar hydrophobic mass in different orientations relative to the pyridinium motif exerts a systematic effect on substrate binding to the OC/H+exchanger. The hydrophobicity of each group of compounds was systematically varied by addition of different substituents at the quaternary nitrogen. Whereas decreases inKiproved to be proportional to hydrophobicity, the position of the phenyl-ring substituent(s) had no effect on substrate interaction with the exchanger. The results led to the development of a preliminary quantitative structure–activity relationship (QSAR) correlating substrate hydrophobicity and substrate binding to the OC/H+exchanger. This QSAR was used to predict the binding of 1-methyl-4-phenylpyridinium (MPP+), (+) and (–)nicotine, (+) and (–)ephedrine, quinine and quinidine to the OC/H+exchanger. Molecular graphics representation of the 3D structures of the test agents was used to develop a working model of a hydrophobic, planar receptor surface on the OC/H+exchanger against which substrates are suggested to interact during binding. Development of the QSAR and receptor surface model open the way to quantitative tests of the specific physical and structural determinants of substrate selectivity by the renal OC/H+exchanger.