Wittinghofer A, Leberman R
Eur J Biochem. 1979 Jan 2;93(1):95-101. doi: 10.1111/j.1432-1033.1979.tb12798.x.
The nucleotide-free elongation factor from Bacillus stearothermophilus provides a means to study the effect of Mg2+ ions on various reactions of the protein. The binding of GDP to the protein is stimulated by Mg2+. From comparative studies with other metal ions, particularly Mn2+, it appears that this stimulation is due to the formation of a metal - GDP complex which is bound to the protein. Protection against proteolysis by trypsin is afforded by both Mg2+ and Mg - GDP, but not by GDP alone. The rate of substitution of the sulphydryl group associated with aminoacyl-tRNA binding, either 5,5'-dithio-bis(2-nitrobenzoic acid) or N-ethylmaleimide is reduced in the presence of Mg2+ - All these observations show that Mg2+ not only is involved in GDP binding but also has a direct effect on the tertiary structure of the protein.
嗜热脂肪芽孢杆菌的无核苷酸延伸因子为研究镁离子对该蛋白质各种反应的影响提供了一种手段。GDP与该蛋白质的结合受到镁离子的刺激。通过与其他金属离子，特别是锰离子的比较研究发现，这种刺激似乎是由于形成了一种与蛋白质结合的金属 - GDP复合物。镁离子和镁 - GDP都能保护该蛋白质免受胰蛋白酶的蛋白水解作用，但单独的GDP则不能。在镁离子存在的情况下，与氨酰 - tRNA结合相关的巯基被5,5'-二硫代双（2-硝基苯甲酸）或N-乙基马来酰亚胺取代的速率降低。所有这些观察结果表明，镁离子不仅参与GDP的结合，而且对该蛋白质的三级结构有直接影响。
