Plant heterotrimeric G proteins are a major group of signaling molecules involved in regulation of critical processes including stress adaptation, seed size, grain quality and immune responses. Despite an abundance of in situ functional studies; purification of the individual subunits of the plant heterotrimer for biophysical and structural characterization and for studies on their interactions are lacking. In this study cloning of the genes encoding the β subunit AGB1 of A. thaliana and its γ-subunits AGG1 and AGG2 using different E. coli expression vectors and screening of expression in several strains are reported. AGB1 could be expressed albeit at very low levels and in all cases it was accompanied by overexpression of E. coli chaperone proteins. AGG1 could only be detected in inclusion body fractions, whereas AGG2 was obtained in soluble fractions and was purified. Purified AGB1 and AGG2 subunits were shown to dimerize in vitro. Further characterization of AGG2 by small angle X-ray scattering measurements and by dynamic light scattering revealed that AGG2 formed homodimers with extended shape in solution. These results are also consistent with those from circular dichroism spectroscopy which yielded 39.4% helical and 50% random coil content for AGG2. This is the first study showing heterologous expression of a plant heterotrimeric G protein β subunit individually and presenting its interaction with a plant γ-subunit in vitro. Results also show that the AGG2 subunit has a disordered structure, which would account for its role in diverse interactions for establishing selectivity in signal propagation.

植物异源三聚体G蛋白是信号传导分子的主要种类，其参与关键过程的调控，包括胁迫适应，种子大小，谷粒质量和免疫反应。尽管进行了大量的原位功能研究；缺乏对植物异源三聚体的各个亚基进行生物物理和结构表征以及对其相互作用进行研究的纯化。在这项研究中，报道了使用不同的大肠杆菌表达载体克隆拟南芥β亚基AGB1及其γ亚基AGG1和AGG2的基因，并筛选了几种菌株中的表达。尽管AGB1的表达水平很低，但在所有情况下都伴随有大肠杆菌的过表达伴侣蛋白。仅在包涵体部分中检测到AGG1，而在可溶性部分中获得AGG2并进行纯化。纯化的AGB1和AGG2亚基显示在体外二聚。通过小角度X射线散射测量和动态光散射对AGG2进行进一步表征，发现AGG2在溶液中形成了具有扩展形状的同型二聚体。这些结果也与圆二色光谱法得出的结果一致，后者的AGG2螺旋含量为39.4％，无规卷曲含量为50％。这是第一个显示植物异源三聚体G蛋白β亚基单独异源表达并在体外显示其与植物γ亚基相互作用的研究。结果还表明，AGG2亚基具有无序结构，