Liao H X, Spremulli L L
Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290.
J Biol Chem. 1990 Aug 15;265(23):13618-22.
The bovine liver mitochondrial factor that promotes the binding of fMet-tRNA to mitochondrial ribosomes, initiation factor 2 (IF-2mt), has been identified in the postribosomal supernatant fraction of isolated liver mitochondria. This factor has been purified approximately 5,000-fold and present preparations are estimated to be about 10% pure. IF-2mt has an apparent molecular weight of about 140,000 as determined by gel filtration chromatography. IF-2mt is active in stimulating fMet-tRNA binding to Escherichia coli ribosomes but E. coli IF-2 is not active in promoting initiator tRNA binding to animal mitochondrial ribosomes. The IF-2mt-mediated binding of fMet-tRNAi(Met) to mitochondrial ribosomes is dependent on the presence of a message such as poly(A,U,G) and on GTP. Nonhydrolyzable analogs of GTP are 2-3-fold less effective in promoting initiation complex formation on mitochondrial ribosomes than is GTP suggesting that IF-2mt is capable of recycling to some extent under the current assay conditions.
促进甲硫氨酰 - tRNA与线粒体核糖体结合的牛肝线粒体因子——起始因子2（IF - 2mt），已在分离的肝线粒体的核糖体后上清液部分中被鉴定出来。该因子已被纯化约5000倍，目前的制剂估计纯度约为10%。通过凝胶过滤色谱法测定，IF - 2mt的表观分子量约为140,000。IF - 2mt在刺激甲硫氨酰 - tRNA与大肠杆菌核糖体结合方面具有活性，但大肠杆菌IF - 2在促进起始tRNA与动物线粒体核糖体结合方面无活性。IF - 2mt介导的甲硫氨酰 - tRNAi(Met)与线粒体核糖体的结合依赖于诸如聚（A，U，G）之类的信使以及GTP的存在。GTP的不可水解类似物在促进线粒体核糖体上起始复合物形成方面的效果比GTP低2 - 3倍，这表明在当前的测定条件下，IF - 2mt能够在一定程度上循环利用。
