Christiansen L, Neirhaus K H
Proc Natl Acad Sci U S A. 1976 Jun;73(6):1839-43. doi: 10.1073/pnas.73.6.1839.
Guanosine tetra- and pentaphosphate, (p)ppGpp, can be synthesized in vitro in a reaction containing only the enzyme (stringent factor), salts, and substrates (nonribosomal system). This reaction is greatly stimulated upon addition of methanol (methanol system) or by ribosomes, mRNA, and tRNA (ribosome system). Here we show that several ribosomal proteins alone stimulate the synthesis of (p)ppGpp in the presence of stringent factor (protein system). The optimal ionic conditions for the ribosome and protein systems are identical. The concentration of ribosomes or any stimulating ribosomal protein required for saturation of a given concentration of stringent factor is similar. Fifty of 54 ribosomal proteins were tested for stimulation in the protein system; 15 proteins showed high activity, seven of these from the 30S ribosomal subunit and eight from the 50S subunit. The physiological relevance of this finding is discussed.
四磷酸鸟苷和五磷酸鸟苷（(p)ppGpp）可在仅含有该酶（严谨因子）、盐和底物的反应体系中体外合成（非核糖体系统）。加入甲醇（甲醇系统）或核糖体、信使核糖核酸（mRNA）及转运核糖核酸（tRNA）（核糖体系统）后，该反应会受到极大刺激。在此我们表明，仅几种核糖体蛋白在存在严谨因子的情况下就能刺激(p)ppGpp的合成（蛋白质系统）。核糖体系统和蛋白质系统的最佳离子条件相同。使给定浓度的严谨因子饱和所需的核糖体或任何具有刺激作用的核糖体蛋白的浓度相似。在蛋白质系统中对54种核糖体蛋白中的50种进行了刺激测试；15种蛋白表现出高活性，其中7种来自30S核糖体亚基，8种来自50S亚基。本文讨论了这一发现的生理相关性。
