Köhler M, Burnashev N, Sakmann B, Seeburg P H
Center for Molecular Biology, Heidelberg University, Germany.
Neuron. 1993 Mar;10(3):491-500. doi: 10.1016/0896-6273(93)90336-p.
GluR6, a subunit of high affinity kainate receptor channels in the mammalian CNS, carries a glutamine (Q) or arginine (R) residue in a critical position (Q/R site) of the putative channel-forming segment TM2. One form, GluR6(Q), is encoded by the GluR6 gene; the other, GluR6(R), is generated by RNA editing. Further analysis of cloned GluR6 cDNA revealed that two additional positions, located in transmembrane segment TM1, are diversified by RNA editing to generate either isoleucine (I) or valine (V) in one and tyrosine (Y) or cysteine (C) in the other TM1 position. In GluR6 channels, in contrast with AMPA receptor channels, the presence of Q in the TM2 Q/R site determines channels with low Ca2+ permeability, whereas an R determines a higher Ca2+ permeability if TM1 is fully edited. In the TM1 unedited form of GluR6, Ca2+ permeability is less dependent on the presence of either Q or R in TM2. Thus Ca2+ permeability of kainate receptor channels can vary, depending on editing of both TM1 and TM2.
GluR6是哺乳动物中枢神经系统中高亲和力红藻氨酸受体通道的一个亚基，在假定的形成通道片段TM2的关键位置（Q/R位点）带有一个谷氨酰胺（Q）或精氨酸（R）残基。一种形式，即GluR6(Q)，由GluR6基因编码；另一种形式，GluR6(R)，则通过RNA编辑产生。对克隆的GluR6 cDNA的进一步分析表明，位于跨膜片段TM1中的另外两个位置也因RNA编辑而多样化，在一个TM1位置产生异亮氨酸（I）或缬氨酸（V），在另一个TM1位置产生酪氨酸（Y）或半胱氨酸（C）。与AMPA受体通道不同，在GluR6通道中，TM2 Q/R位点存在Q决定了低Ca2+通透性的通道，而如果TM1被完全编辑，R则决定了更高的Ca2+通透性。在GluR6的TM1未编辑形式中，Ca2+通透性对TM2中Q或R的存在依赖性较小。因此，红藻氨酸受体通道的Ca2+通透性会有所不同，这取决于TM1和TM2的编辑情况。
