Department of Biochemistry, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.
J Mol Biol. 2011 Oct 21;413(2):372-89. doi: 10.1016/j.jmb.2011.08.017. Epub 2011 Aug 29.
The RGK family of small G-proteins, including Rad, Gem, Rem1, and Rem2, is inducibly expressed in various mammalian tissues and interacts with voltage-dependent calcium channels and Rho kinase. Many questions remain regarding their physiological roles and molecular mechanism. Previous crystallographic studies reported RGK G-domain:guanosine di-phosphate structures. To test whether RGK proteins undergo a nucleotide-induced conformational change, we determined the crystallographic structures of Rad:GppNHp and Rem2:GppNHp to 1.7 and 1.8 Å resolutions, respectively. Also, we characterized the nucleotide-binding properties and conformations for Gem, Rad, and several structure-based mutants using fluorescence spectroscopy. The results suggest that RGK G-proteins may not behave as Ras-like canonical nucleotide-induced molecular switches. Further, the RGK proteins have differing structures and nucleotide-binding properties, which may have implications for their varied action on effectors.
RGK 家族的小分子 G 蛋白，包括 Rad、Gem、Rem1 和 Rem2，在各种哺乳动物组织中可诱导表达，并与电压依赖性钙通道和 Rho 激酶相互作用。关于它们的生理作用和分子机制，仍有许多问题尚待解决。先前的晶体学研究报道了 RGK G 结构域：鸟苷二磷酸结构。为了测试 RGK 蛋白是否经历核苷酸诱导的构象变化，我们分别以 1.7 和 1.8Å 的分辨率确定了 Rad：GppNHp 和 Rem2：GppNHp 的晶体结构。此外，我们还使用荧光光谱法对 Gem、Rad 和几种基于结构的突变体的核苷酸结合特性和构象进行了表征。结果表明，RGK G 蛋白可能不像 Ras 样经典核苷酸诱导的分子开关那样发挥作用。此外，RGK 蛋白具有不同的结构和核苷酸结合特性，这可能对它们对效应器的不同作用有影响。
