Zong X, Zucker H, Hofmann F, Biel M
Institut für Pharmakologie und Toxikologie, Technische Universität München, Germany.
EMBO J. 1998 Jan 15;17(2):353-62. doi: 10.1093/emboj/17.2.353.
The activation of cyclic nucleotide-gated (CNG) channels is a complex process comprising the initial ligand binding and a consecutive allosteric transition from a closed to an open configuration. The cone and olfactory CNG channels differ considerably in cyclic nucleotide affinity and efficacy. In each channel, the cyclic nucleotide-binding site is connected to the last transmembrane segment of the channel by a linker peptide (C-linker) of approximately 90 amino acids. Here we report that replacement of three amino acids in the cone C-linker by the corresponding amino acids of the olfactory channel (I439V, D481A and D494S) profoundly enhanced the cAMP efficacy and increased the affinities for cAMP and cGMP. Unlike the wild-type cone channel, the mutated channel exhibited similar single-channel kinetics for both cGMP and cAMP, explaining the increase in cAMP efficacy. We thus conclude that the identified amino acids are major determinants of channel gating.
环核苷酸门控（CNG）通道的激活是一个复杂的过程，包括初始配体结合以及随后从关闭构象到开放构象的变构转变。视锥细胞和嗅觉CNG通道在环核苷酸亲和力和效能方面有很大差异。在每个通道中，环核苷酸结合位点通过一个约90个氨基酸的连接肽（C-连接肽）与通道的最后一个跨膜片段相连。在此我们报告，将视锥细胞C-连接肽中的三个氨基酸替换为嗅觉通道的相应氨基酸（I439V、D481A和D494S），可显著增强cAMP效能，并增加对cAMP和cGMP的亲和力。与野生型视锥细胞通道不同，突变通道对cGMP和cAMP表现出相似的单通道动力学，这解释了cAMP效能的增加。因此我们得出结论，所鉴定的氨基酸是通道门控的主要决定因素。
