Corry Ben, Vora Taira, Chung Shin-Ho
Chemistry, School of Biomedical and Chemical Sciences, The University of Western Australia, Crawley, WA, 6009, Australia.
Biochim Biophys Acta. 2005 Jun 1;1711(1):72-86. doi: 10.1016/j.bbamem.2005.03.002. Epub 2005 Mar 24.
We examine how a variety of cationic channels discriminate between ions of differing charge. We construct models of the KcsA potassium channel, voltage gated sodium channel and L-type calcium channel, and show that they all conduct monovalent cations, but that only the calcium channel conducts divalent cations. In the KcsA and sodium channels divalent ions block the channel and prevent any further conduction. We demonstrate that in each case, this discrimination and some of the more complex conductance properties of the channels is a consequence of the electrostatic interaction of the ions with the charges in the channel protein. The KcsA and sodium channels bind divalent ions strongly enough that they cannot be displaced by other ions and thereby block the channel. On the other hand, the calcium channel binds them less strongly such that they can be destabilized by the repulsion of another incoming divalent ion, but not by the lesser repulsion from monovalent ions.
我们研究了多种阳离子通道如何区分不同电荷的离子。我们构建了KcsA钾通道、电压门控钠通道和L型钙通道的模型，并表明它们都能传导单价阳离子，但只有钙通道能传导二价阳离子。在KcsA和钠通道中，二价离子会阻塞通道并阻止进一步传导。我们证明，在每种情况下，这种区分以及通道一些更复杂的传导特性是离子与通道蛋白中的电荷发生静电相互作用的结果。KcsA和钠通道对二价离子的结合力很强，以至于它们不会被其他离子取代从而阻塞通道。另一方面，钙通道对它们的结合力较弱，以至于它们会被另一个进入的二价离子的排斥作用破坏稳定，但不会被单价离子较小的排斥作用破坏稳定。
