IDENTIFICATION OF CHANNEL SITES ON G BETA GAMMA SUBUNITS

第一个例子是G蛋白门控的内向整流钾(GIRK)通道 指一种蛋白质，其功能受到直接相互作用的调节 与GTP结合(G)蛋白的β亚基结合(Logothetis等， 1987)。在这个FIRCA中，他们建议确定Gβ亚基中的区域(S) 与GIRK频道互动的(S)。而Gbeta1-beta4可以激活GIRK 具有类似效率的通道，Gbeta5即使显示了 完整的表情。他们将在Gbeta1和Gbeta5之间使用嵌合策略 以确定两个异构体之间负责 它们刺激GIRK活性的能力存在差异。他们已经这样做了 将范围缩小到95个氨基酸，他们将进一步缩小范围 区域使用类似的嵌合方法，以便通过站点定向 他们可以确定特定的氨基酸残基负责 两个β亚基之间的功能差异。使用删除 突变方法他们将尝试确定最小的Gbeta区域 能够绑定通道。具有影响作用的Gβ多肽的设计 通道活动将在确定最小Gbeta区域之后进行。

The G protein-gated inwardly rectifying K+ (GIRK) channel was the first example of a protein whose function was shown to be regulated by direct interactions with the betagamma subunits of GTP-binding (G) proteins (Logothetis et al., 1987). In this FIRCA they proposed to identify the region(s) in Gbeta subunits that interact(s) with GIRK channels. While Gbeta1-beta4 can activate GIRK channels with similar efficiency, Gbeta5 fails to do so even though it shows intact expression. They will use a chimeric strategy between Gbeta1 and Gbeta5 to identify the region between the two isoforms that is responsible for the difference in their abilities to stimulate GIRK activity. As they have already narrowed the region down to 95 amino acids, they will further narrow down this region utilizing a similar chimeric approach, so that through site-directed mutagenesis they can identify the specific amino acid residues responsible for the functional differences between the two beta subunits. Using a deletion mutagenesis approach they will attempt to identify the minimal Gbeta regions capable of binding the channel. Design of Gbeta peptides capable of affecting channel activity will follow identification of the minimal Gbeta regions.