Structural specificity of chloroquine-hematin binding related to inhibition of hematin polymerization and parasite growth.
Structural specificity of chloroquine-hematin binding related to inhibition of hematin polymerization and parasite growth.
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DOI：
10.1021/jm9902180
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发表时间：
1999-10
影响因子：
7.3
通讯作者：
S. Vippagunta;A. Dorn;H. Matile;A. Bhattacharjee;J. Karle;W. Ellis;R. Ridley;J. Vennerstrom
中科院分区：
文献类型：
--
作者：
S. Vippagunta;A. Dorn;H. Matile;A. Bhattacharjee;J. Karle;W. Ellis;R. Ridley;J. Vennerstrom
大量数据支持寄生虫食物液泡中氯喹(CQ)-血素结合导致血素聚合抑制和血素中毒导致寄生虫死亡的假设。为了更好地了解CQ-血素结合的结构特异性，我们选择了13个CQ类似物，并测量了它们的血素结合亲和力、抑制血素聚合和抑制寄生虫生长。通过等温滴定量热法（ITC）测定，化学计量学数据和放热结合焓表明，与CQ一样，这些类似物与两种或两种以上的血红素-氧二聚体结合形成共面pi-pi三明治型络合物。与CQ的4.0 × 10(5) M（-1）相比，关联常数（K(a) s）的范围为0.46至2.9 × 10(5) M（-1）。值得注意的是，我们无法测量血红素mu-氧二聚体与CQ的6-氯类似物11之间的任何显著相互作用。这一结果表明，CQ中的7-氯取代基是其与血红素mu-氧二聚体结合亲和力的关键结构决定因素。分子模拟实验强化了这样的观点，即在CQ-血红蛋白mu-氧二聚体中观察到的焓有利的pi-pi相互作用源于CQ和血红蛋白mu-氧二聚体在分子间接触点的面外pi电子密度的有利排列。对于与CQ相关的4-氨基喹啉，我们的数据表明，喹啉环7位的吸电子官能团是抑制血素聚合和寄生虫生长的活性所必需的，并且7位的氯取代是最佳的。我们的结果也证实了CQ二氨基烷基侧链，特别是脂肪族叔氮原子，是CQ耐药的重要结构决定因素。对于CQ类似物1-13，K(a)与血红素聚合IC（50）值之间缺乏相关性表明，CQ-血红素mu-氧二聚体复合物的其他性质，而不是其单独的结合常数，在抑制血红素聚合中起作用。然而，当血素聚合IC（50）值归一化血素mu-氧二聚体结合亲和力时，抑制血素聚合与抑制寄生虫生长之间存在适度的相关性，进一步证明抗疟药4-氨基喹啉类药物通过这种机制起作用。
Considerable data now support the hypothesis that chloroquine (CQ)-hematin binding in the parasite food vacuole leads to inhibition of hematin polymerization and parasite death by hematin poisoning. To better understand the structural specificity of CQ-hematin binding, 13 CQ analogues were chosen and their hematin binding affinity, inhibition of hematin polymerization, and inhibition of parasite growth were measured. As determined by isothermal titration calorimetry (ITC), the stoichiometry data and exothermic binding enthalpies indicated that, like CQ, these analogues bind to two or more hematin mu-oxo dimers in a cofacial pi-pi sandwich-type complex. Association constants (K(a)'s) ranged from 0.46 to 2.9 x 10(5) M(-1) compared to 4.0 x 10(5) M(-1) for CQ. Remarkably, we were not able to measure any significant interaction between hematin mu-oxo dimer and 11, the 6-chloro analogue of CQ. This result indicates that the 7-chloro substituent in CQ is a critical structural determinant in its binding affinity to hematin mu-oxo dimer. Molecular modeling experiments reinforce the view that the enthalpically favorable pi-pi interaction observed in the CQ-hematin mu-oxo dimer complex derives from a favorable alignment of the out-of-plane pi-electron density in CQ and hematin mu-oxo dimer at the points of intermolecular contact. For 4-aminoquinolines related to CQ, our data suggest that electron-withdrawing functional groups at the 7-position of the quinoline ring are required for activity against both hematin polymerization and parasite growth and that chlorine substitution at position 7 is optimal. Our results also confirm that the CQ diaminoalkyl side chain, especially the aliphatic tertiary nitrogen atom, is an important structural determinant in CQ drug resistance. For CQ analogues 1-13, the lack of correlation between K(a) and hematin polymerization IC(50) values suggests that other properties of the CQ-hematin mu-oxo dimer complex, rather than its association constant alone, play a role in the inhibition of hematin polymerization. However, there was a modest correlation between inhibition of hematin polymerization and inhibition of parasite growth when hematin polymerization IC(50) values were normalized for hematin mu-oxo dimer binding affinities, adding further evidence that antimalarial 4-aminoquinolines act by this mechanism.