Tichelaar Willem, Safferling Markus, Keinänen Kari, Stark Holger, Madden Dean R
Ion Channel Structure Group, Max Planck Institute for Medical Research, Jahnstr. 29, D-69120 Heidelberg, Germany.
J Mol Biol. 2004 Nov 19;344(2):435-42. doi: 10.1016/j.jmb.2004.09.048.
The ionotropic glutamate receptors (iGluRs) represent a major family of ion channels whose quaternary structure has not yet been defined. Here, we present the three-dimensional structure of a fully assembled iGluR, determined at approximately 20A resolution by electron microscopy. Analysis of negatively stained single-particle images reveals the presence of 2-fold, but not 4-fold, symmetry for these tetrameric channels, providing the first direct structural evidence for a dimer-of-dimers assembly. The receptor appears elongated, measuring approximately 170Ax140Ax110A, with the 2-fold symmetry centered on its longitudinal axis. The overall molecular shape and symmetry suggest an orientation relative to the membrane and permit the identification of a putative transmembrane domain. Internal cavities located along the longitudinal axis may represent components of the ion conduction pathway.
离子型谷氨酸受体（iGluRs）是离子通道的一个主要家族，其四级结构尚未明确。在此，我们展示了一个完全组装好的iGluR的三维结构，通过电子显微镜以约20埃的分辨率确定。对负染单颗粒图像的分析揭示了这些四聚体通道存在2倍对称性，但不存在4倍对称性，为二聚体组装提供了首个直接的结构证据。该受体呈细长形，尺寸约为170埃×140埃×110埃，2倍对称中心位于其纵轴上。整体分子形状和对称性表明了其相对于膜的取向，并有助于识别一个假定的跨膜结构域。沿纵轴分布的内部腔可能代表离子传导途径的组成部分。
