Stereochemistry of Glutamate Receptor Agonist Efficacy: Engineering a Dual-Specificity AMPA/Kainate Receptor

详细信息    查看全文

• 作者：Dean R. Madden ; Qing Cheng ; Shalita Thiran ; Shanti Rajan ; Frank Rigo ; Kari Keinä ; nen ; Stefan Reinelt ; Herbert Zimmermann ; and Vasanthi Jayaraman
• 刊名：Biochemistry
• 出版年：2004
• 出版时间：December 21, 2004
• 年：2004
• 卷：43
• 期：50
• 页码：15838 - 15844
• 全文大小：106K
• 年卷期：v.43,no.50(December 21, 2004)
• ISSN：1520-4995

文摘

Upon agonist binding, the bilobate ligand-binding domains of the ionotropic glutamate receptors(iGluR) undergo a cleft closure whose magnitude correlates broadly with the efficacy of the agonist.AMPA (rs/alpha.gif" BORDER=0>-amino-5-methyl-3-hydroxy-4-isoxazolepropionic acid) and kainate are nonphysiological agoniststhat distinguish between subsets of iGluR. Kainate acts with low efficacy at AMPA receptors. Here wereport that the structure-based mutation L651V converts the GluR4 AMPA receptor into a dual-specificityAMPA/kainate receptor fully activated by both agonists. To probe the stereochemical basis of partialagonism, we have also investigated the correlation between agonist efficacy and a series of vibrationaland fluorescence spectroscopic signals of agonist binding to the corresponding wild-type and mutant GluR4ligand-binding domains. Two signals track the extent of channel activation: the maximal change in intrinsictryptophan fluorescence and the environment of the single non-disulfide bonded C426, which appears toprobe the strength of interactions with the ligand rs/alpha.gif" BORDER=0>-amino group. Both of these signals arise from functionalgroups that are poised to detect changes in the extent of channel cleft closure and thus provide additionalinformation about the coupling between conformational changes in the ligand-binding domain and activationof the intact receptor.