Grigorjev P A, Bezrukov S M
Institute of Biological Physics, Russian Academy of Sciences, Puschino.
Biophys J. 1994 Dec;67(6):2265-71. doi: 10.1016/S0006-3495(94)80711-8.
We have studied the anion-dependent gating of roflamycoin ion channels using spectral analysis of noise in currents through multichannel planar lipid bilayers. We have found that in addition to low frequency current fluctuations that may be attributed to channel switching between open and closed conformations, roflamycoin channels exhibit a pronounced higher frequency noise indicating that the open channel conductance has substates with short lifetimes. This noise is well described by a Lorentzian spectrum component with a characteristic cutoff frequency that depends on the type of halide anions according to their position in the Hofmeister series. It is suggested that transitions between the substates correspond to a reversible ionization of the channel by a penetrating anion that binds to the channel structure, more chaotropic anions being bound for longer times. Within a framework of a two-substate model, the duration of the substate with reduced electrostatic barrier for cation current varies exponentially with anion electron polarizability. This explains two features of the roflamycoin channel reported earlier: the increase in apparent single-channel conductance along the series F- < Cl- < Br- < I- and the reverse of channel selectivity from anionic for KF to cationic for KI.
我们利用通过多通道平面脂质双层的电流噪声的频谱分析，研究了罗氟米考因离子通道的阴离子依赖性门控。我们发现，除了可能归因于通道在开放和关闭构象之间切换的低频电流波动外，罗氟米考因通道还表现出明显的高频噪声，这表明开放通道电导具有寿命较短的亚态。这种噪声可以用具有特征截止频率的洛伦兹频谱分量很好地描述，该截止频率根据卤化物阴离子在霍夫迈斯特序列中的位置而取决于其类型。有人认为，亚态之间的转变对应于穿透性阴离子与通道结构结合导致的通道可逆电离，更具离液序列高的阴离子结合时间更长。在双亚态模型的框架内，阳离子电流静电势垒降低的亚态持续时间随阴离子电子极化率呈指数变化。这解释了先前报道的罗氟米考因通道的两个特征：沿F- < Cl- < Br- < I-序列表观单通道电导增加，以及通道选择性从对KF为阴离子型转变为对KI为阳离子型。
