Probing the geometry of the inner vestibule of BK channels with sugars.
Probing the geometry of the inner vestibule of BK channels with sugars.
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DOI：
10.1085/jgp.200509286
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发表时间：
2005-08
期刊：
影响因子：
--
通讯作者：
Magleby KL
中科院分区：
文献类型：
--
作者：
Brelidze TI;Magleby KL
通过检测细胞内液中不同糖对单通道电流幅度(单位电流)的影响，探讨BK通道内前庭的几何构型。甘油、葡萄糖和蔗糖以浓度和大小依赖的方式减少通过BK通道的单位电流，其顺序为蔗糖、葡萄糖和甘油，外向电流的减少大于内向电流的减少。外向电流的减少与糖所占据的流体动力学体积的分数比渗透压的变化更直接地相关。对于浓度为1M的糖，有糖和无糖时的外向电流I/V图叠加后，K+I从15 0 mm增加到2 M时，I/V图的幅度增加，而对标度曲线的形状影响不大。这些观察表明，糖≤1M主要通过进入内前庭和减少K+通过前庭的移动来减少外向电流，而不是通过限制K+进入前庭的扩散控制的通路。在2M蔗糖作用下，K+进入前庭的扩散受限于150 mM K+I和电压+100 mV。K+i的增加缓解了扩散的限制。根据在内部前厅入口处没有负电荷环的通道的5pA扩散限制电流，估计捕获半径为2.2ó。加上水合K+的半径(6-8？)，就得到了8-10？的内部前庭入口的有效半径。这样一个功能上很宽的内前庭入口，再加上我们观察到内前庭中即使少量的糖浓度也会减少单位电流，表明BK通道的大电导需要一个较宽的内前庭。
The geometry of the inner vestibule of BK channels was probed by examining the effects of different sugars in the intracellular solution on single-channel current amplitude (unitary current). Glycerol, glucose, and sucrose decreased unitary current through BK channels in a concentration- and size-dependent manner, in the order sucrose > glucose > glycerol, with outward currents being reduced more than inward currents. The fractional decrease of outward current was more directly related to the fractional hydrodynamic volume occupied by the sugars than to changes in osmolality. For concentrations of sugars ≤1 M, the i/V plots for outward currents in the presence and absence of sugar superimposed after scaling, and increasing K+ i from 150 mM to 2 M increased the magnitudes of the i/V plots with little effect on the shape of the scaled curves. These observations suggest that sugars ≤1 M reduce outward currents mainly by entering the inner vestibule and reducing the movement of K+ through the vestibule, rather than by limiting diffusion-controlled access of K+ to the vestibule. With 2 M sucrose, the movement of K+ into the inner vestibule became diffusion limited for 150 mM K+ i and voltages >+100 mV. Increasing K+ i then relieved the diffusion limitation. An estimate of the capture radius based on the 5 pA diffusion-limited current for channels without the ring of negative charge at the entrance to the inner vestibule was 2.2 Å. Adding the radius of a hydrated K+ (6–8 Å) then gave an effective radius for the entrance to the inner vestibule of 8–10 Å. Such a functionally wide entrance to the inner vestibule together with our observation that even small concentrations of sugar in the inner vestibule reduce unitary current suggest that a wide inner vestibule is required for the large conductance of BK channels.
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DOI：
10.1085/jgp.59.4.388
发表时间：
1972-04
期刊：
The Journal of general physiology
影响因子：
--
作者：
Armstrong CM;Hille B
通讯作者：
Hille B
影响因子：
56.9
作者：
Doyle, DA;Cabral, JM;MacKinnon, R
通讯作者：
MacKinnon, R
DOI：
10.1085/jgp.58.4.413
发表时间：
1971-10
期刊：
The Journal of general physiology
影响因子：
--
作者：
Armstrong CM
通讯作者：
Armstrong CM
影响因子：
2.9
作者：
ARAKAWA, T;TIMASHEFF, SN
通讯作者：
TIMASHEFF, SN
DOI：
10.1085/jgp.20028756
发表时间：
2003-02
期刊：
The Journal of general physiology
影响因子：
--
作者：
Consiglio JF;Andalib P;Korn SJ
通讯作者：
Korn SJ