Department of Neurochemistry, Max-Planck Institute for Brain Research, 60528 Frankfurt, Germany.
Biochem Biophys Res Commun. 2011 Jul 15;410(4):737-43. doi: 10.1016/j.bbrc.2011.06.024. Epub 2011 Jun 12.
Channelrhodopsin 2 (ChR2) is a microbial-type rhodopsin with a putative heptahelical structure that binds all-trans-retinal. Blue light illumination of ChR2 activates an intrinsic leak channel conductive for cations. Sequence comparison of ChR2 with the related ChR1 protein revealed a cluster of charged amino acids within the predicted transmembrane domain 2 (TM2), which includes glutamates E90, E97 and E101. Charge inversion substitutions of these residues significantly altered ChR2 function as revealed by two-electrode voltage-clamp recordings of light-induced currents from Xenopus laevis oocytes expressing the respective mutant proteins. Specifically, replacement of E90 by lysine or alanine resulted in differential effects on H(+)- and Na(+)-mediated currents. Our results are consistent with this glutamate side chain within the proposed TM2 contributing to ion flux through and the cation selectivity of ChR2.
通道视紫红质 2（ChR2）是一种微生物型视紫红质，具有假定的七螺旋结构，可结合全反式视黄醛。ChR2 的蓝光照射激活了对阳离子具有固有渗漏通道的内在渗漏通道。ChR2 与相关的 ChR1 蛋白的序列比较揭示了预测的跨膜域 2（TM2）内带电荷的氨基酸簇，其中包括谷氨酸 E90、E97 和 E101。这些残基的电荷反转取代通过表达相应突变蛋白的非洲爪蟾卵母细胞的双电极电压钳记录光诱导电流明显改变了 ChR2 的功能。具体而言，用赖氨酸或丙氨酸取代 E90 导致对 H(+)和 Na(+)介导电流的不同影响。我们的结果与 TM2 中谷氨酸侧链有助于 ChR2 的离子通量和阳离子选择性的假设一致。
