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首页> 外文期刊>Biochemistry >IONOPHORE 4-BRA23187 TRANSPORTS ZN2+ AND MN2+ WITH HIGH SELECTIVITY OVER CA2+
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IONOPHORE 4-BRA23187 TRANSPORTS ZN2+ AND MN2+ WITH HIGH SELECTIVITY OVER CA2+

机译：IONOPHORE 4-BRA23187在CA2 +上具有高选择性的传输ZN2 +和MN2 +

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摘要

The cation transport selectivities of the Ca2+ ionophores A23187, Ionomycin, and 4-BrA23187 have been determined using a model system comprised of phospholipid vesicles loaded with the chelator/indicator Quin-2. At pH 7.00 and a 100 mu M concentration of the cations, A23187 displays the transport selectivity sequence Zn2+ > Mn2+ > Ca2+ > Co2+ > Ni2+ > Sr2+, With the absolute rates of transport spanning similar to 3 orders of magnitude. Similar data are obtained with Ionomycin, although the relative transport rates of Zn2+ and Mn2+ are equivalent, and the range of absolute rates is decreased by a factor of similar to 3. When values are normalized to those of Ca2+, transport selectivity is seen to be only weakly related to complexation or extraction selectivity. It is also seen that, when used to manipulate Ca2+ (or Mg2+), both ionophores can be expected to alter the distribution of additional divalent cations which have known biological activities. 4-BrA23187 is a low-activity ionophore for Ca2+, compared to A23187 and Ionomycin, while retaining comparable activities as an ionophore for the other cations. As a consequence, 4-BrA23187 is highly selective for the transport of Zn2+ and Mn2+, compared to Ca2+, with selectivity ratios approaching that of valinomycin for K+ over Naf when conditions are optimal. Plots of the log of the rate of cation transport vs the log of the ionophore concentration indicate that Ca2+ is transported primarily as a 2:1 complex by A23187 and 4-BrA23187, but Zn2+ and Mn2+ are transported, in part, as 1:1 complexes. These findings, together with a postulated low stability of 2:1, compared to 1:1 complexes between 4-BrA23187 and divalent cations, partially explain the novel transport selectivity of this compound. Unlike A23187 or Ionomycin, 4-BrA23187 may be useful for investigating cell regulation by Zn2+ and Mn2+, without interference by regulatory mechanisms which respond to Ca2+.
机译：已使用包含负载螯合剂/指示剂Quin-2的磷脂囊泡的模型系统确定了Ca2 +离子载体A23187，碘霉素和4-BrA23187的阳离子转运选择性。在pH 7.00和100μM的阳离子浓度下，A23187显示的运输选择性序列为Zn2 +> Mn2 +> Ca2 +> Co2 +> Ni2 +> Sr2 +，绝对运输速率跨越了三个数量级。尽管Zn2 +和Mn2 +的相对传输速率相等，并且绝对速率的范围减小了约3，但与碘菌霉素也获得了相似的数据。当将值标准化为Ca2 +的值时，可以看到传输选择性为仅与络合或萃取选择性弱相关。还可以看出，当用于操纵Ca2 +（或Mg2 +）时，可以预期两个离子载体都会改变具有已知生物活性的其他二价阳离子的分布。与A23187和依诺霉素相比，4-BrA23187是低活性的Ca2 +离子载体，同时保留了与其他阳离子类似的离子载体活性。结果，与Ca2 +相比，4-BrA23187对Zn2 +和Mn2 +的运输具有高度选择性，并且在最佳条件下，对Na +而言，其对K +的选择性比接近于缬霉素。阳离子迁移率对数与离子载体浓度对数的关系图表明，Ca2 +主要通过A23187和4-BrA23187以2：1络合物的形式运输，但Zn2 +和Mn2 +的一部分以1：1的形式运输复合体。与4-BrA23187和二价阳离子之间的1：1配合物相比，这些发现以及假定的2：1的低稳定性，部分解释了该化合物的新型转运选择性。与A23187或碘霉素不同，4-BrA23187可用于研究Zn2 +和Mn2 +对细胞的调控，而不受对Ca2 +响应的调控机制的干扰。

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