Natochin M, Gasimov K G, Artemyev N O
Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.
Biochemistry. 2001 May 1;40(17):5322-8. doi: 10.1021/bi015505w.
A novel Galpha binding consensus sequence, termed G-protein regulatory (GPR) or GoLoco motif, has been identified in a growing number of proteins, which are thought to modulate G-protein signaling. Alternative roles of GPR proteins as nucleotide exchange factors or as GDP dissociation inhibitors for Galpha have been proposed. We investigated the modulation of the GDP/GTP exchange of Gialpha(1), Goalpha, and Gsalpha by three proteins containing GPR motifs (GPR proteins), LGN-585-642, Pcp2, and RapIGAPII-23-131, to elucidate the mechanisms of GPR protein function. The GPR proteins displayed similar patterns of interaction with Gialpha(1) with the following order of affinities: Gialpha(1)GDP >> Gialpha(1)GDPAlF(4)(-) > or = Gialpha(1)GTPgammaS. No detectable binding of the GPR proteins to Gsalpha was observed. LGN-585-642, Pcp2, and RapIGAPII-23-131 inhibited the rates of spontaneous GTPgammaS binding and blocked GDP release from Gialpha(1) and Goalpha. The inhibitory effects of the GPR proteins on Gialpha(1) were significantly more potent, indicating that Gi might be a preferred target for these modulators. Our results suggest that GPR proteins are potent GDP dissociation inhibitors for Gialpha-like Galpha subunits in vitro, and in this capacity they may inhibit GPCR/Gi protein signaling in vivo.
在越来越多的蛋白质中发现了一种新的Gα结合共有序列，称为G蛋白调节（GPR）或GoLoco基序，这些蛋白质被认为可调节G蛋白信号传导。有人提出GPR蛋白作为核苷酸交换因子或Gα的GDP解离抑制剂具有其他作用。我们研究了三种含有GPR基序的蛋白质（GPR蛋白）LGN-585-642、Pcp2和RapIGAPII-23-131对Gα1、Goα和Gsα的GDP/GTP交换的调节作用，以阐明GPR蛋白的功能机制。GPR蛋白与Gα1的相互作用模式相似，亲和力顺序如下：Gα1GDP >> Gα1GDPAlF4(-) ≥ Gα1GTPγS。未观察到GPR蛋白与Gsα有可检测到的结合。LGN-585-642、Pcp2和RapIGAPII-23-131抑制了自发的GTPγS结合速率，并阻止了GDP从Gα1和Goα释放。GPR蛋白对Gα1的抑制作用明显更强，表明Gi可能是这些调节剂的首选靶点。我们的结果表明，GPR蛋白在体外是Gα样Gα亚基的有效GDP解离抑制剂，并且以这种能力它们可能在体内抑制GPCR/Gi蛋白信号传导。
