Covalently linked gramicidin channels: effects of linker hydrophobicity and alkaline metals on different stereoisomers.
Covalently linked gramicidin channels: effects of linker hydrophobicity and alkaline metals on different stereoisomers.
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共价连接的短杆菌肽通道：连接体疏水性和碱金属对不同立体异构体的影响。
DOI：
10.1016/s0006-3495(01)76151-6
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发表时间：
2001
影响因子：
3.4
通讯作者：
Cukierman,S
中科院分区：
文献类型：
--
作者：
Armstrong,KM;Quigley,EP;Quigley,P;Crumrine,DS;Cukierman,S
的二氧戊环基团上的门控和单通道电导的不同立体异构体的二氧戊环连接短杆菌肽A（gA）通道重建在平面脂质双层的直接作用进行了研究。合成了四种不同的共价连接的gA二聚体。在其中两个中，接头是先前描述的常规二氧戊环（SS和RR通道）。两个gA共价连接一个新的修改二氧戊环基团含有视网膜附件（ret-SS和ret-RR gA二聚体）。这些蛋白质也形成了脂质双层中的离子通道，并对一价阳离子具有选择性。庞大的疏水性视黄酸基团的存在将二氧戊环连接基固定在双层核心中，防止其旋转到孔的亲水性内腔中。在1 M HCl的门控动力学的SS或RR二聚体是无法区分的视网膜同行;在SS和ret-SS的开放和关闭状态的停留时间分布基本相同。特别是，RR的失活并没有被视网膜组的存在所阻止。它的结论是，无论是在SS或RR二聚体的快速关闭事件，也不是RR的失活可能是一个功能性的后果翻转的二氧戊环内的孔的通道。另一方面，RR二聚体的失活完全消除时，碱金属（Cs+或K+）的渗透阳离子的通道。事实上，RR通道的开放状态变得非常稳定，SS和RR通道的门控特性与之前渗透质子的情况不同。与HCl中一样，在二氧戊环连接体中存在视黄醛不会影响SS和RR在含Cs+或K+溶液中的门控行为。有关门控连接GA二聚体的替代假设进行了讨论。
The direct role of the dioxolane group on the gating and single-channel conductance of different stereoisomers of the dioxolane-linked gramicidin A (gA) channels reconstituted in planar lipid bilayers was investigated. Four different covalently linked gA dimers were synthesized. In two of them, the linker was the conventional dioxolane described previously (SS and RR channels). Two gAs were covalently linked with a novel modified dioxolane group containing a retinal attachment (ret-SS and ret-RR gA dimers). These proteins also formed ion channels in lipid bilayers and were selective for monovalent cations. The presence of the bulky and hydrophobic retinal group immobilizes the dioxolane linker in the bilayer core preventing its rotation into the hydrophilic lumen of the pore. In 1M HCl the gating kinetics of the SS or RR dimers were indistinguishable from their retinal counterparts; the dwell-time distributions of the open and closed states in the SS and ret-SS were basically the same. In particular, the inactivation of the RR was not prevented by the presence of the retinal group. It is concluded that neither the fast closing events in the SS or RR dimers nor the inactivation of the RR are likely to be a functional consequence of the flipping of the dioxolane inside the pore of the channel. On the other hand, the inactivation of the RR dimer was entirely eliminated when alkaline metals (Cs+or K+) were the permeating cations in the channel. In fact, the open state of the RR channel became extremely stable, and the gating characteristics of both the SS and RR channels were different from what was seen before with permeating protons. As in HCl, the presence of a retinal in the dioxolane linker did not affect the gating behavior of the SS and RR in Cs+- or K+-containing solutions. Alternative hypotheses concerning the gating of linked gA dimers are discussed.