Translation initiation factor IF2 interacts with the 30 S ribosomal subunit via two separate binding sites
Translation initiation factor IF2 interacts with the 30 S ribosomal subunit via two separate binding sites
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DOI：
10.1016/j.jmb.2006.07.043
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发表时间：
2006-09-29
影响因子：
5.6
通讯作者：
Gualerzi, Claudio O.
中科院分区：
文献类型：
--
作者：
Caserta, Enrico;Tomsic, Jerneja;Gualerzi, Claudio O.
比较分析了大肠杆菌翻译起始因子IF 2的两种天然形式（IF 2 α和IF 2 β）和缺乏前294个残基（对应于整个N-末端结构域）的因子的N-末端缺失突变体（1F 2 Delta N）的功能特性。结果显示，IF 2 α和IF 2 β显示出几乎不可区分的性质，而IF 2 δ N虽然在翻译起始途径的所有步骤中都具有完全活性，但显示出具有与完整分子明显不同的性质和要求的功能活性。事实上，与IF 2 α和IF 2 β不同，IF 2 δ N与30 S亚基的结合、fMet-tRNA与核糖体结合的IF 2 δ N依赖性刺激和起始二肽形成强烈依赖于IF 1和GTP的存在。目前的研究结果表明，使用两个独立的活性位点，IF 2建立了两个相互作用的30 S核糖体亚基具有不同的性质和功能。位于IF 2的N结构域中的第一个位点负责将因子“锚定”到亚基的高亲和力相互作用，而主要位于与EF-G和EF-Tu的结构域II同源的β-桶模块中的第二个位点负责IF 2的功能（“核心”）相互作用，导致30 S亚基P-位点中fMet-tRNA的解码。第一种相互作用是功能性的，对离子强度变化敏感，对鸟苷酸配体的性质和IF 1的存在基本上不敏感，不像第二种相互作用强烈依赖于IF 1和GTP的存在。(c)2006爱思唯尔有限公司版权所有。
The functional properties of the two natural forms of Escherichia coli translation initiation factor IF2 (IF2 alpha and IF2 beta) and of an N-terminal deletion mutant of the factor (1F2 Delta N) lacking the first 294 residues, corresponding to the entire N-terminal domain, were analysed comparatively. The results revealed that IF2 alpha and IF2 beta display almost indistinguishable properties, whereas IF2 Delta N, although fully active in all steps of the translation initiation pathway, displays functional activities having properties and requirements distinctly different from those of the intact molecule. Indeed, binding of IF2 Delta N to the 30 S subunit, IF2 Delta N-dependent stimulation of fMet-tRNA binding to the ribosome and of initiation dipeptide formation strongly depend upon the presence of IF1 and GTP, unlike with IF2 alpha and IF2 beta. The present results indicate that, using two separate active sites, IF2 establishes two interactions with the 30S ribosomal subunit which have different properties and functions. The first site, located in the N domain of IF2, is responsible for a high-affinity interaction which "anchors" the factor to the subunit while the second site, mainly located in the beta-barrel module homologous to domain II of EF-G and EF-Tu, is responsible for the functional ("core") interaction of IF2 leading to the decoding of fMet-tRNA in the 30 S subunit P-site. The first interaction is functionally dispensable, sensitive to ionic-strength variations and essentially insensitive to the nature of the guanosine nucleotide ligand and to the presence of IF1, unlike the second interaction which strongly depends upon the presence of IF1 and GTP. (c) 2006 Elsevier Ltd. All rights reserved.