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首页> 外文期刊>Molecular and Cellular Biology >Identification of Domains and Residues within the ? Subunit of Eukaryotic Translation Initiation Factor 2B (eIF2B?) Required for Guanine Nucleotide Exchange Reveals a Novel Activation Function Promoted by eIF2B Complex Formation
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Identification of Domains and Residues within the ? Subunit of Eukaryotic Translation Initiation Factor 2B (eIF2B?) Required for Guanine Nucleotide Exchange Reveals a Novel Activation Function Promoted by eIF2B Complex Formation

机译：识别域中的域和残基？鸟嘌呤核苷酸交换所需的真核翻译起始因子2B（eIF2B？）亚基揭示了由eIF2B复合物形成促进的新型激活功能。

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Eukaryotic translation initiation factor 2B (eIF2B) is the guanine nucleotide exchange factor for protein synthesis initiation factor 2 (eIF2). Composed of five subunits, it converts eIF2 from a GDP-bound form to the active eIF2-GTP complex. This is a regulatory step of translation initiation. In vitro, eIF2B catalytic function can be provided by the largest (epsilon) subunit alone (eIF2B?). This activity is stimulated by complex formation with the other eIF2B subunits. We have analyzed the roles of different regions of eIF2B? in catalysis, in eIF2B complex formation, and in binding to eIF2 by characterizing mutations in the Saccharomyces cerevisiaegene encoding eIF2B? (GCD6) that impair the essential function of eIF2B. Our analysis of nonsense mutations indicates that the C terminus of eIF2B? (residues 518 to 712) is required for both catalytic activity and interaction with eIF2. In addition, missense mutations within this region impair the catalytic activity of eIF2B? without affecting its ability to bind eIF2. Internal, in-frame deletions within the N-terminal half of eIF2B? disrupt eIF2B complex formation without affecting the nucleotide exchange activity of eIF2B? alone. Finally, missense mutations identified within this region do not affect the catalytic activity of eIF2B? alone or its interactions with the other eIF2B subunits or with eIF2. Instead, these missense mutations act indirectly by impairing the enhancement of the rate of nucleotide exchange that results from complex formation between eIF2B? and the other eIF2B subunits. This suggests that the N-terminal region of eIF2B? is an activation domain that responds to eIF2B complex formation.
机译：真核翻译起始因子2B（eIF2B）是蛋白质合成起始因子2（eIF2）的鸟嘌呤核苷酸交换因子。它由五个亚基组成，将eIF2从GDP绑定形式转换为活动的eIF2-GTP复合体。这是翻译起始的调控步骤。在体外，eIF2B的催化功能可以由最大的（ε）亚基单独提供（eIF2Bα）。与其他eIF2B亚基的复杂形成刺激了这种活性。我们已经分析了eIF2B不同区域的作用？在催化中，在eIF2B复合体形成中以及通过表征编码eIF2B的啤酒酵母基因中的突变来与eIF2结合？ （ GCD6 ）损害了eIF2B的基本功能。我们对无意义突变的分析表明，eIF2B的C末端是α-末端。 （残基518至712）对于催化活性和与eIF2的相互作用都是必需的。另外，该区域内的错义突变会损害eIF2Bα的催化活性。而不影响其结合eIF2的能力。 eIF2B N末端一半内的内部框内缺失？在不影响eIF2B核苷酸交换活性的情况下破坏eIF2B复合物的形成？单独。最后，在该区域内鉴定出的错义突变不会影响eIF2B？的催化活性。单独或与其他eIF2B亚基或与eIF2的相互作用。相反，这些错义突变通过削弱由eIF2Bβ之间的复杂形成而导致的核苷酸交换速率的提高而间接起作用。和其他eIF2B亚基。这表明eIF2B的N-末端区域？是响应eIF2B复合物形成的激活域。

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