Observing a model ion channel gating action in model cell membranes in real time in situ: membrane potential change induced alamethicin orientation change.
Observing a model ion channel gating action in model cell membranes in real time in situ: membrane potential change induced alamethicin orientation change.
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DOI：
10.1021/ja2110784
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发表时间：
2012-04-11
影响因子：
15
通讯作者：
Chen, Zhan
中科院分区：
文献类型：
--
作者：
Ye, Shuji;Li, Hongchun;Wei, Feng;Jasensky, Joshua;Boughton, Andrew P.;Yang, Pei;Chen, Zhan
离子通道在活细胞的运输和调节功能中起着至关重要的作用。了解这些通道的门控机制对于理解和治疗与离子通道相关的疾病非常重要。一种用于研究离子通道门控机制的潜在模型肽是丙甲霉素，其采用分裂α/310螺旋结构并响应于电势的变化。在这项研究中，和频产生振动光谱（SFG-VS），辅以衰减全反射傅里叶变换红外光谱（ATR-FTIR），已被应用到丙甲霉素（模型较大的通道蛋白）和1-棕榈酰-2-油酰-sn-甘油-3-磷酸胆碱（POPC）脂质双层之间的相互作用，在跨膜电位的存在下。通过改变与双层接触的溶液的pH来控制膜电位差，并使用荧光光谱法进行测量。丙甲霉素在POPC脂质双层的取向角，然后确定在不同的pH值下使用偏振SFG酰胺I光谱。假设所有分子均采用相同的取向（δ分布），则在pH=6.7时，N末端的α螺旋和C末端的310螺旋相对于表面法线分别倾斜约72°（θ1）和50°（θ2）。当pH增加到11.9时，θ1和θ2分别减小到56.5°和45°。使用SFG和ATR-FTIR测量的组合验证了δ分布假设，其显示在两种pH条件下θ1角的分布相当窄。这表明在POPC脂质双层中，表面上的所有丙甲霉素分子采用几乎相同的取向。局部pH值的变化，在接近的双层调节膜电位，从而诱导减少的倾斜和弯曲角的两个螺旋在丙甲霉素。这是首次报道的应用SFG模型离子通道门控机制的研究模型细胞膜。
Ion channels play crucial roles in transport and regulatory functions of living cells. Understanding the gating mechanisms of these channels is important to understanding and treating diseases that have been linked to ion channels. One potential model peptide for studying the mechanism of ion channel gating is alamethicin, which adopts a split alpha/310 helix structure and responds to changes in electric potential. In this study, sum frequency generation vibrational spectroscopy (SFG-VS), supplemented by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), has been applied to characterize interactions between alamethicin (a model for larger channel proteins) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayers in the presence of an electric potential across the membrane. The membrane potential difference was controlled by changing the pH of the solution in contact with the bilayer, and measured using fluorescence spectroscopy. The orientation angle of alamethicin in POPC lipid bilayers was then determined at different pH values using polarized SFG amide I spectra. Assuming that all molecules adopt the same orientation (a δ distribution), at pH=6.7 the α-helix at the N-terminus and the 310 helix at the C-terminus tilt at about 72° (θ1) and 50° (θ2) versus the surface normal, respectively. When pH increases to 11.9, θ1 and θ2 decrease to 56.5° and 45°, respectively. The δ distribution assumption was verified using a combination of SFG and ATR-FTIR measurements, which showed a quite narrow distribution in the angle of θ1 for both pH conditions. This indicates that all alamethicin molecules at the surface adopt a nearly identical orientation in POPC lipid bilayers. The localized pH change in proximity to the bilayer modulates the membrane potential and thus induces a decrease in both the tilt and bend angles of the two helices in alamethicin. This is the first reported application of SFG to the study of model ion channel gating mechanisms in model cell membranes.
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影响因子：
56.9
作者：
Doyle, DA;Cabral, JM;MacKinnon, R
通讯作者：
MacKinnon, R
影响因子：
2.9
作者：
BANERJEE, U;ZIDOVETZKI, R;CHAN, SI
通讯作者：
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影响因子：
15
作者：
Fu, Li;Ma, Gang;Yan, Elsa C. Y.
通讯作者：
Yan, Elsa C. Y.
影响因子：
3.8
作者：
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通讯作者：
Luchian, Tudor
影响因子：
3.9
作者：
Doyle, AW;Fick, J;Neivandt, DJ
通讯作者：
Neivandt, DJ