Liao H X, Spremulli L L
Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290.
J Biol Chem. 1990 Jul 15;265(20):11761-5.
The mRNA for cytochrome oxidase subunit II (CoII) from bovine mitochondria binds to the small subunit of the mitochondrial ribosome in the absence of auxiliary factors. The synthetic polymer poly(U) is effective in competing with CoII mRNA for binding, although the polymer poly(A,U,G) competes very weakly. The effects of mRNA length on the interaction between the 28 S ribosomal subunit and mRNA have been examined using truncated derivatives of CoII mRNA. These results indicate that there is a minimum length of approximately 400 nucleotides required for the efficient binding of the mRNA to the small subunit. Shorter mRNAs will bind, but do so with much lower association constants. mRNAs of various lengths but with reduced secondary structure were prepared by substituting ITP for GTP during in vitro transcription reactions. These derivatives show the same effects of length as do the normal mRNA, indicating that RNA secondary structure is not a critical factor in subunit-mRNA interaction. The binding of the mRNA to the 28 S subunit is not influenced by the presence of guanine nucleotides or by the presence of a triphosphate at the 5' end of the RNA.
来自牛线粒体的细胞色素氧化酶亚基II（CoII）的信使核糖核酸（mRNA）在没有辅助因子的情况下，能与线粒体核糖体的小亚基结合。合成聚合物聚尿嘧啶（poly(U)）能有效地与CoII mRNA竞争结合，尽管聚合物聚（A,U,G）的竞争作用非常微弱。利用CoII mRNA的截短衍生物，研究了mRNA长度对28 S核糖体亚基与mRNA之间相互作用的影响。这些结果表明，mRNA与小亚基有效结合所需的最短长度约为400个核苷酸。较短的mRNA也能结合，但结合的缔合常数要低得多。在体外转录反应中用次黄苷三磷酸（ITP）取代鸟苷三磷酸（GTP），制备了各种长度但二级结构减少的mRNA。这些衍生物显示出与正常mRNA相同的长度效应，表明RNA二级结构不是亚基-mRNA相互作用的关键因素。mRNA与28 S亚基的结合不受鸟嘌呤核苷酸的存在或RNA 5'端三磷酸的存在的影响。
