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首页> 外文期刊>Nucleic acids research >Roles of yeast eIF2α and eIF2β subunits in the binding of the initiator methionyl-tRNA
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Roles of yeast eIF2α and eIF2β subunits in the binding of the initiator methionyl-tRNA

机译：酵母eIF2α和eIF2β亚基在启动子甲硫氨酰-tRNA结合中的作用

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摘要

Heterotrimeric eukaryotic/archaeal translation initiation factor 2 (e/aIF2) binds initiator methionyl-tRNA and plays a key role in the selection of the start codon on messenger RNA. tRNA binding was extensively studied in the archaeal system. The γ subunit is able to bind tRNA, but the α subunit is required to reach high affinity whereas the β subunit has only a minor role. In Saccharomyces cerevisiae however, the available data suggest an opposite scenario with β having the most important contribution to tRNA-binding affinity. In order to overcome difficulties with purification of the yeast eIF2γ subunit, we designed chimeric eIF2 by assembling yeast α and β subunits to archaeal γ subunit. We show that the β subunit of yeast has indeed an important role, with the eukaryote-specific N- and C-terminal domains being necessary to obtain full tRNA-binding affinity. The α subunit apparently has a modest contribution. However, the positive effect of α on tRNA binding can be progressively increased upon shortening the acidic C-terminal extension. These results, together with small angle X-ray scattering experiments, support the idea that in yeast eIF2, the tRNA molecule is bound by the α subunit in a manner similar to that observed in the archaeal aIF2–GDPNP–tRNA complex.
机译：异源三聚体真核/古细菌翻译起始因子2（e / aIF2）结合起始子甲硫氨酸-tRNA，并在信使RNA的起始密码子选择中起关键作用。在古细菌系统中广泛研究了tRNA结合。 γ亚基能够结合tRNA，但需要α亚基才能达到高亲和力，而β亚基的作用很小。然而，在酿酒酵母中，可用数据提示了一种相反的情况，其中β对tRNA结合亲和力的贡献最大。为了克服酵母eIF2γ亚基纯化的困难，我们通过将酵母α和β亚基组装到古细菌γ亚基上来设计嵌合eIF2。我们显示酵母的β亚基确实具有重要作用，真核生物特异的N和C末端域对于获得完整的tRNA结合亲和力是必不可少的。 α亚基显然具有适度的贡献。但是，在缩短酸性C端延伸时，α对tRNA结合的积极作用会逐渐增强。这些结果与小角度X射线散射实验一起，支持了以下观点：在酵母eIF2中，tRNA分子被α亚基结合，其方式类似于在古细菌aIF2-GDPNP-tRNA复合物中观察到的方式。

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