Characterization of chloroquine-hematin mu-oxo dimer binding by isothermal titration calorimetry.
Characterization of chloroquine-hematin mu-oxo dimer binding by isothermal titration calorimetry.
复制标题
通过等温滴定量热法表征氯喹-血红素 mu-氧二聚体结合。
DOI：
10.1016/s0304-4165(00)00058-1
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
Vennerstrom,JL
中科院分区：
文献类型：
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作者：
Vippagunta,SR;Dorn,A;Ridley,RG;Vennerstrom,JL
大量研究表明，氯喹（CQ）抗疟疾活性的一个关键特征是它与血素的相互作用。我们现在用等温滴定量热法（ITC）详细描述了cq -血红素相互作用。在pH 5.6 ~ 9.0之间，焓驱动的cq -血红素μ-氧二聚体结合的结合常数（kavales）在2.3-4.4×105M−1的狭窄范围内下降。因此，cq -血红素μ-氧二聚体的结合亲和力在寄生虫食物液泡的pH范围（4.8-5.4）内可能不会降低。结合亲和力不受高盐浓度的影响，表明离子相互作用对这种络合作用没有显著贡献。随着离子强度的增加，cq -血红素μ-氧二聚体结合的熵罚减小，同时血红素μ-氧二聚体聚集增加。在pH 6.5 ~ 9.0范围内，CQ的化学计量(n)为1:4，表明CQ与两种血红素μ-氧二聚体结合。在pH 5.6下，1:8的化学计量表明CQ与四种血红素μ-氧二聚体结合。这项工作进一步证明了CQ通过使血凝素单体-血凝素μ-氧二聚体平衡正向移动，从而阻碍血凝素单体与血凝素的结合，从而导致可溶性血凝素在寄生虫体内的破坏性积累，并导致血凝素中毒死亡。
Numerous studies indicate that a key feature of chloroquine’s (CQ) antimalarial activity is its interaction with hematin. We now characterize this CQ–hematin interaction in detail using isothermal titration calorimetry (ITC). Between pH 5.6 and 9.0, association constants (Kavalues) for enthalpy-driven CQ–hematin μ-oxo dimer binding fell in the narrow range of 2.3–4.4×105M−1. It is therefore probable that CQ–hematin μ-oxo dimer binding affinity does not diminish at the pH range (4.8–5.4) of the parasite food vacuole. The binding affinity was unaffected by high salt concentrations, suggesting that ionic interactions do not contribute significantly to this complexation. With increasing ionic strength, the entropic penalty of CQ–hematin μ-oxo dimer binding decreased accompanied by increased hematin μ-oxo dimer aggregation. A stoichiometry (n) of 1:4 in the pH range 6.5–9.0 indicates that CQ binds to two hematin μ-oxo dimers. At pH 5.6, a stoichiometry of 1:8 suggests that CQ binds to an aggregate of four hematin μ-oxo dimers. This work adds further evidence supporting the hypothesis that CQ impedes hematin monomer incorporation into hemozoin by producing a forward shift in the hematin monomer-hematin μ-oxo dimer equilibrium, contributing to a destructive accumulation of soluble forms of hematin in the parasite and leading to its death by hematin poisoning.