Bilayer thickness modulates the conductance of the BK channel in model membranes.
Bilayer thickness modulates the conductance of the BK channel in model membranes.
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DOI：
10.1529/biophysj.103.029678
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发表时间：
2004-06
影响因子：
3.4
通讯作者：
C. Yuan;R. O'connell;P. Feinberg-Zadek;L. Johnston;S. Treistman
中科院分区：
文献类型：
--
作者：
C. Yuan;R. O'connell;P. Feinberg-Zadek;L. Johnston;S. Treistman
在由POPE/POPS（3.3：1）或POPE/POPS与添加的20%SPM（3.3：1：1）、CER（3.3：1：1）或CHL（3.3：1：1）制成的重构双层中评价BK通道的电导。SPM的存在，这是已知的增加双层厚度，显着降低了BK通道的电导。为了直接测试膜厚度的作用，在由具有增加长度的酰基链（C14：1-C24：1）的PC形成的双层中测量BK通道的电导，所有这些都是在不存在SPM的情况下。斜率电导最大的链长（C18：1）和更薄（C14：1）和更厚（C24：1）的双层大大减少，表明膜厚度单独可以修改斜率电导。此外，在一个简化的二元混合物的DOPE/SPM，形成一个封闭的，相分离的双层，BK通道的测量电导显示出明确的双峰分布。相比之下，添加CER（其具有类似于SPM的酰基链结构，但没有其庞大的极性头部基团到POPE/POPS中）没有效果，添加CHL也是如此。用AFM检查由这些相同的脂质混合物制成的膜的表面结构。SPM和CER的掺入导致POPE/POPS单层中微区的形成，但只有SPM促进了相应双层中观察到的高相量的大幅增加。CHL的加入消除了POPE/POPS双层中观察到的相分离。因此，将SPM掺入POPE/POPS膜中观察到的通道电导的降低归因于较大的SPM富集域，其比相邻的双层更厚。
The conductance of the BK channel was evaluated in reconstituted bilayers made of POPE/POPS (3.3:1), or POPE/POPS with an added 20% of either SPM (3.3:1:1), CER (3.3:1:1), or CHL (3.3:1:1). The presence of SPM, which is known to increase bilayer thickness, significantly reduced the conductance of the BK channel. To directly test the role of membrane thickness, the conductance of the BK channel was measured in bilayers formed from PCs with acyl chains of increasing length (C14:1-C24:1), all in the absence of SPM. Slope conductance was maximal at a chain length of (C18:1) and much reduced for both thinner (C14:1) and thicker (C24:1) bilayers, indicating that membrane thickness alone can modify slope conductance. Further, in a simplified binary mixture of DOPE/SPM that forms a confined, phase-separated bilayer, the measured conductance of BK channels shows a clear bimodal distribution. In contrast, the addition of CER, which has an acyl chain structure similar to SPM but without its bulky polar head group to POPE/POPS, was without effect, as was the addition of CHL. The surface structure of membranes made from these same lipid mixtures was examined with AFM. Incorporation of both SPM and CER resulted in the formation of microdomains in POPE/POPS monolayers, but only SPM promoted a substantial increase in the amount of the high phase observed for the corresponding bilayers. The addition of CHL to POPE/POPS eliminated the phase separation observed in the POPE/POPS bilayer. The decrease in channel conductance observed with the incorporation of SPM into POPE/POPS membranes was, therefore, attributed to larger SPM-rich domains that appear thicker than the neighboring bilayer.