The R6A-1 peptide binds to switch II of Galphai1 but is not a GDP-dissociation inhibitor.
The R6A-1 peptide binds to switch II of Galphai1 but is not a GDP-dissociation inhibitor.
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R6A-1 肽与 Galphai1 的开关 II 结合，但不是 GDP 解离抑制剂。
DOI：
10.1016/j.bbrc.2005.11.132
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Siderovski,DavidP
中科院分区：
文献类型：
--
作者：
Willard,FrancisS;Siderovski,DavidP
异源三聚体G蛋白是将来自膜受体的信号转化为细胞内生理变化的分子开关。近年来，已经分离出几种与异源三聚体G蛋白α亚基结合的肽，包括新的Gαi1·GDP结合肽R6 A和KB-752。R6 A肽及其最小化衍生物R6 A-1与Gαi1·GDP相互作用。基于对BODIPYFL-GTPγS与Gαi1结合的光谱分析，已报道R6 A-1具有Gαi1的鸟嘌呤核苷酸解离抑制剂（GDI）活性[W. W.是的，R.W. Roberts，Biochemistry 43（28）（2004）9265-9275]。利用放射性配体结合，我们表明R6 A-1不是Gα i1亚基的GDI。此外，我们证明R6 A-1降低了Gαi1-BODIPYFL-GTPγS复合物的荧光量子产率，从而解释了先前报道的作为荧光伪影的GDI活性。我们进一步表明，R6 A-1与鸟嘌呤核苷酸交换因子肽KB-752具有显著的序列相似性，该肽与Gαi1的开关II结合。我们使用竞争结合分析表明R6 A-1也结合Gα亚基的开关II。
Heterotrimeric G-proteins are molecular switches that convert signals from membrane receptors into changes in intracellular physiology. Recently, several peptides that bind heterotrimeric G-protein α subunits have been isolated including the novel Gαi1·GDP binding peptides R6A and KB-752. The R6A peptide and its minimized derivative R6A-1 interact with Gαi1·GDP. Based on spectroscopic analysis of BODIPYFL-GTPγS binding to Gαi1, it has been reported that R6A-1 has guanine nucleotide dissociation inhibitor (GDI) activity against Gαi1[W.W. Ja, R.W. Roberts, Biochemistry 43 (28) (2004) 9265–9275]. Using radioligand binding, we show that R6A-1 is not a GDI for Gαi1subunits. Furthermore, we demonstrate that R6A-1 reduces the fluorescence quantum yield of the Gαi1–BODIPYFL-GTPγS complex, thus explaining the previously reported GDI activity as a fluorescence artifact. We further show that R6A-1 has significant sequence similarity to the guanine nucleotide exchange factor peptide KB-752 that binds to switch II of Gαi1. We use competitive binding analysis to show that R6A-1 also binds to switch II of Gα subunits.