Schneggenburger R, Ascher P
Ecole Normale Supérieure, Laboratoire de Neurobiologie, Paris, France.
Neuron. 1997 Jan;18(1):167-77. doi: 10.1016/s0896-6273(01)80055-6.
We report a strong coupling between permeation and gating in a mutant NMDA channel (NR1 N598Q-NR2A). The channel opens to two states that differ by their conductance and, surprisingly, by their selectivity for two permeant monovalent cations, Na+ and Cs+. The two open states are linked to the closed state via a cyclic gating reaction that proceeds preferentially in one direction under biionic conditions, indicating that the gating mechanism is not at equilibrium. The direction and the magnitude of this gating asymmetry can be accounted for by assuming that ions bound to a site in the permeation pathway influence the gating of this mutant channel, and that in the closed state, the channel site is accessible to internal cations.
我们报道了一种突变型NMDA通道（NR1 N598Q-NR2A）中渗透与门控之间的强耦合。该通道开放为两种状态，这两种状态在电导率上有所不同，令人惊讶的是，在对两种渗透性单价阳离子Na⁺和Cs⁺的选择性上也有所不同。这两种开放状态通过一种循环门控反应与关闭状态相连，在双离子条件下，该反应优先沿一个方向进行，这表明门控机制并非处于平衡状态。这种门控不对称性的方向和幅度可以通过假设渗透途径中一个位点结合的离子影响该突变通道的门控，以及在关闭状态下，通道位点可被内部阳离子接近来解释。
