Structure analysis of multi-factor complex of eukaryotic translation initiation factor

对于所有生物来说，基因表达调控是其环境适应、发育和分化等生物学过程中的重要调控机制。翻译是基因表达的最后一步，它可以分为三个不同的阶段：起始、延伸和终止。启动是这些阶段中最复杂的，涉及最多的调控过程，都由30多个因子(EIF)和核糖体执行。在这一阶段的调控允许对细胞应激(饥饿、热休克、病毒感染)或细胞凋亡做出即时和快速的反应，并控制细胞在记忆、发育和分化等生物学过程中的活动水平。翻译起始的基本过程是将eIF1、eIF2-GTP、eIF3、eIF5和Met-tRNA1I组装成多因子复合体(MFC)，将MFC与核糖体小亚基(43S)结合，然后结合…更多的5‘末端的mRNA到43S，并扫描mRNA以识别所产生的48S复合体上的起始密码子。在本研究中，主要针对eIF2对MFC的功能和结构进行了分析。特别是分析了组装过程中各组分的构象变化和相互作用，以了解翻译启动的反应机理和规律。去年，我们解决了a/eif2βγ和a/eif2βγ-gdp复合体的结构。根据所获得的结构，对α/eif2βγ进行了功能分析。考虑到a/eif2γ与翻译延伸因子EF-Tu在结构和功能上的同源性，a/eif2γ的Switch1基序可能与EF-Tu类似，在结合和释放Met-tRNA方面发挥着重要作用。在本研究中，获得的a/eif2βγ-Gdp复合体的结构表明，a/eif2β与a/eif2βγ的Switch1基序相互作用，从而使Switch1基序位于远离GDP结合位点的位置。此外，还发现了a/eif2βγ和a/eif2βγ-gdp、a/eif2βγ和a/eif2γ结构之间的开关1区域的构象变化。因此，我们对Switch1基序的保守残基进行了突变，并检测了这些突变对Met-tRNA^I结合的影响。论文已提交。较少

For all living organisms, the regulation of gene expression is an important control mechanism in their biological processes such as environmental adaptation, development, and differentiation. The translation is the final step in the flow of the gene expression, and it can be divided into three distinct phases : initiation, elongation and termination. Initiation is most complex of these phases and involves greatest number of regulatory processes that all performed by more than 30 factors (eIFs) and ribosome. The regulation at this phase allows for immediate and rapid response to cellular stress (starvation, heat shock, virus infection) or apoptosis, and controls the cellular activity level in their biological processes such as memory, development, and differentiation. The fundamental processes in translation initiation are the assembling components of eIF1, eIF2-GTP, eIF3, eIF5, and Met-tRNA^i to a multi-factor complex (MFC), binding MFC to ribosomal small subunit (43S) and then binding … More 5'end of mRNA to 43S, and scanning mRNA to recognize the start codon on the resulting 48S complex. In this study, the functional and structural analysis of MFC mainly on eIF2 was focused. Especially, conformation changes and interaction of the components during assemble were analyzed for understanding the reaction mechanism and regulation of translation initiation. Last year, we have solved the structures of a/eIF2βγ and a/eIF2βγ-GDP complex. Based on the obtained structures the functional analysis of a/eIF2βγ was carried out this year.Considering the structural and functional homology between a/eIF2γ and translation elongation factor EF-Tu, switch1 motif of a/eIF2γ may play an important role in binding and releasing Met-tRNA^i similarly to that of EF-Tu. In this study, the obtained structure of a/eIF2βγ-GDP complex showed that a/eIF2β was interacted with switch1 motif of a/eIF2βγ and consequently switch1 motif was positioned in the distant from GDP-binding site. Moreover, conformation changes of switch1 region between the structures of a/eIF2βγ and a/eIF2βγ-GDP, and a/eIF2βγ and a/eIF2γ were found. Therefore, we mutated conserved residues of switch1 motif, and inspected the effect of these mutations on Met-tRNA^i binding. The paper was in submitted. Less