大鼠连接蛋白43间隙连接通道的单价离子选择性序列。
Monovalent ion selectivity sequences of the rat connexin43 gap junction channel.
作者信息
Wang H Z, Veenstra R D
机构信息
Department of Pharmacology, SUNY Health Science Center at Syracuse, 13210, USA.
出版信息
J Gen Physiol. 1997 Apr;109(4):491-507. doi: 10.1085/jgp.109.4.491.
The relative permeability sequences of the rat connexin 43 (rCx43) gap junction channel to seven cations and chloride were examined by double whole cell patch clamp recording of single gap junction channel currents in rCx43 transfected neuroblastoma 2A (N2A) cell pairs. The measured maximal single channel slope conductances (gammaj, in pS) of the junctional current-voltage relationships in 115 mM XCI were RbC1 (103) > or = CsC1 (102) > KC1 (97) > NaC1 (79) > or = LiC1 (78) > TMAC1 (65) > TEAC1 (53) and for 115 mM KY were KBr (105) > KC1 (97) > Kacetate (77) > Kglutamate (61). The single channel conductance- aqueous mobility relationships for the test cations and anions were linear. However, the predicted minimum anionic and cationic conductances of these plots did not accurately predict the rCx43 channel conductance in 115 mM KC1. Instead, the conductance of the rCx43 channel in 115 mM KC1 was accurately predicted from cationic and anionic conductance-mobility plots by applying a mobility scaling factor Dx/Do, which depends upon the relative radii of the permeant ions to an estimated pore radius. Relative permeabilities were determined for all of the monovalent catious and anions tested from asymmetric salt reversal potential measurements and the Goldman-Hodgkin-Katz voltage equation. These experiments estimate the relative chloride to potassium permeability to be 0.13. The relationship between the relative cation permeability and hydrated radius was modeled using the hydrodynamic equation assuming a pore radius of 6.3 +/- 0.4 A. Our data quantitatively demonstrate that the rCx43 gap junction channel is permeable to monovalent atomic and organic cations and anions and the relative permeability sequences are consistent with an Eisenman sequence II or I, respectively. These predictions about the rCx43 channel pore provide a useful basis for future investigations into the structural determinants of the conductance and permeability properties of the connexin channel pore.
通过双全细胞膜片钳记录转染了大鼠连接蛋白43（rCx43）的神经母细胞瘤2A（N2A）细胞对中的单个缝隙连接通道电流，检测了大鼠连接蛋白43（rCx43）缝隙连接通道对七种阳离子和氯离子的相对通透性序列。在115 mM XCI中，测得的连接电流-电压关系的最大单通道斜率电导（γj，单位为pS）为：RbC1（103）≥CsC1（102）＞KC1（97）＞NaC1（79）≥LiC1（78）＞TMAC1（65）＞TEAC1（53）；在115 mM KY中为：KBr（105）＞KC1（97）＞K醋酸盐（77）＞K谷氨酸盐（61）。测试阳离子和阴离子的单通道电导-水相迁移率关系呈线性。然而，这些图预测的最小阴离子和阳离子电导并不能准确预测115 mM KC1中rCx43通道的电导。相反，通过应用迁移率缩放因子Dx/Do，从阳离子和阴离子电导-迁移率图中可以准确预测115 mM KC1中rCx43通道的电导，该因子取决于渗透离子的相对半径与估计的孔半径。通过不对称盐反转电位测量和戈德曼-霍奇金- Katz电压方程确定了所有测试的单价阳离子和阴离子的相对通透性。这些实验估计氯离子与钾离子的相对通透性为0.13。使用流体动力学方程，假设孔半径为6.3±0.4 Å，对相对阳离子通透性与水合半径之间的关系进行了建模。我们的数据定量表明，rCx43缝隙连接通道对单价原子和有机阳离子及阴离子具有通透性，相对通透性序列分别与艾森曼序列II或I一致。这些关于rCx43通道孔的预测为未来研究连接蛋白通道孔的电导和通透性特性的结构决定因素提供了有用的基础。
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