Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290, USA.
Biochem Biophys Res Commun. 2010 Jan 1;391(1):942-6. doi: 10.1016/j.bbrc.2009.11.169. Epub 2009 Dec 5.
Polyamines are important in both prokaryotic and eukaryotic translational systems. Spermine is a quaternary aliphatic amine that is cationic under physiological conditions. In this paper, we demonstrate that spermine stimulates fMet-tRNA binding to mammalian mitochondrial 55S ribosomes. The stimulatory effect of spermine is independent of the identity of the mRNA. The degree of stimulation of spermine is the same at all concentrations of mitochondrial initiation factor 2 (IF2(mt)) and mitochondrial initiation factor 3 (IF3(mt)). This observation indicates that IF2(mt) and IF3(mt), while essential for initiation, are not the primary components of the translation initiation system affected by spermine. IF3(mt) dissociates 55S ribosomes detectably in the absence of spermine, but this effect is strongly inhibited in the presence of spermine. This observation indicates that the positive effect of spermine on initiation is not due to an increase in the availability of the small subunits for initiation. Spermine also promotes fMet-tRNA binding to small subunits of the mitochondrial ribosome in the presence of IF2(mt). The major effect of spermine in promoting initiation complex formation thus appears to be on the interaction of fMet-tRNA with the ribosome.
多胺在原核和真核翻译系统中都很重要。亚精胺是一种带正电荷的季铵脂肪族胺，在生理条件下呈阳离子状态。在本文中，我们证明亚精胺刺激 fMet-tRNA 与哺乳动物线粒体 55S 核糖体结合。亚精胺的刺激作用与 mRNA 的身份无关。在所有浓度的线粒体起始因子 2（IF2(mt)）和线粒体起始因子 3（IF3(mt)）下，亚精胺的刺激程度相同。这一观察结果表明，IF2(mt)和 IF3(mt)虽然对起始是必需的，但不是受亚精胺影响的翻译起始系统的主要成分。IF3(mt)在没有亚精胺的情况下可检测到与 55S 核糖体解离，但在亚精胺存在下，这种效应被强烈抑制。这一观察结果表明，亚精胺对起始的正效应不是由于小亚基起始的可用性增加。亚精胺也促进 fMet-tRNA 在 IF2(mt)存在下与线粒体核糖体的小亚基结合。因此，亚精胺促进起始复合物形成的主要作用似乎是在 fMet-tRNA 与核糖体的相互作用上。
