Abramson R D, Browning K S, Dever T E, Lawson T G, Thach R E, Ravel J M, Merrick W C
Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106.
J Biol Chem. 1988 Apr 15;263(11):5462-7.
Three mammalian eukaryotic initiation factors (eIF) are required for the ATP-dependent binding of mRNA to the 40 S ribosomal subunit. These three factors, eIF-4A, eIF-4B, and eIF-4F, have also been isolated from wheat germ. Three assays were used to measure the ability of the wheat germ factors to interact with and/or substitute for the mammalian factors. Two assay systems were used to measure partial reactions involving the interaction of the three factors, ATP, and mRNA: 1) RNA-dependent ATP hydrolysis and 2) cross-linking of the factors to the 5' cap of oxidized mRNA. A third assay system was used to measure the ability of the factors to support initiation of protein synthesis. The results of the ATP hydrolysis and cross-linking experiments indicate that the wheat germ factors can interact with or substitute for the mammalian factors. Wheat germ eIF-4A appears to be functionally equivalent to mammalian eIF-4A. Wheat germ eIF-4B and eIF-4F appear to be isozymes possessing functions similar to mammalian eIF-4F. Wheat germ eIF-4B does not appear to be a functional equivalent to the mammalian eIF-4B. In a complete translation system from wheat germ, mammalian factors partially substitute for wheat germ factors, whereas the wheat germ factors are ineffective in the mammalian system.
mRNA与40S核糖体亚基的ATP依赖性结合需要三种哺乳动物真核起始因子（eIF）。这三种因子，即eIF-4A、eIF-4B和eIF-4F，也已从小麦胚芽中分离出来。使用三种测定方法来衡量小麦胚芽因子与哺乳动物因子相互作用和/或替代哺乳动物因子的能力。使用两种测定系统来测量涉及这三种因子、ATP和mRNA相互作用的部分反应：1）RNA依赖性ATP水解和2）因子与氧化mRNA的5'帽的交联。第三种测定系统用于测量这些因子支持蛋白质合成起始的能力。ATP水解和交联实验的结果表明，小麦胚芽因子可以与哺乳动物因子相互作用或替代哺乳动物因子。小麦胚芽eIF-4A在功能上似乎等同于哺乳动物eIF-4A。小麦胚芽eIF-4B和eIF-4F似乎是具有与哺乳动物eIF-4F相似功能的同工酶。小麦胚芽eIF-4B在功能上似乎不等同于哺乳动物eIF-4B。在来自小麦胚芽的完整翻译系统中，哺乳动物因子部分替代小麦胚芽因子，而小麦胚芽因子在哺乳动物系统中无效。
