Abramson R D, Dever T E, Merrick W C
Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106.
J Biol Chem. 1988 May 5;263(13):6016-9.
The role of eukaryotic initiation factor (eIF)4B in translation is somewhat uncertain, although it appears to stimulate a variety of activities of eIF-4A and eIF-4F. Using the model RNA-dependent ATP hydrolysis assay, the ability of eIF-4B to stimulate eIF-4A and eIF-4F was investigated. The most dramatic effect of eIF-4B is to increase the affinity of eIF-4A for RNA; no effect is seen on the affinity of eIF-4A for ATP. This is not the case for eIF-4F where stimulation occurs primarily through an increase in Vmax and not a change in the affinity for RNA. The finding that eIF-4A and eIF-4B can bind to an mRNA (lacking in secondary structure), with essentially the same degree of effectiveness and affinity as would occur for natural mRNAs in the presence of eIF-4A, eIF-4B, and eIF-4F, suggests a possible role for eIF-4A and eIF-4B in both cap-independent and internal initiation.
真核生物起始因子（eIF）4B在翻译过程中的作用尚不完全明确，尽管它似乎能刺激eIF-4A和eIF-4F的多种活性。利用依赖RNA的ATP水解分析模型，对eIF-4B刺激eIF-4A和eIF-4F的能力进行了研究。eIF-4B最显著的作用是增加eIF-4A与RNA的亲和力；而对eIF-4A与ATP的亲和力没有影响。eIF-4F的情况则不同，其刺激主要通过Vmax的增加，而不是对RNA亲和力的改变。eIF-4A和eIF-4B能够与缺乏二级结构的mRNA结合，其有效性和亲和力与在eIF-4A、eIF-4B和eIF-4F存在时天然mRNA的情况基本相同，这一发现表明eIF-4A和eIF-4B在不依赖帽结构起始和内部起始过程中可能发挥作用。
