Characterization of the minimal catalytic domain within eIF2B: the guanine-nucleotide exchange factor for translation initiation
Characterization of the minimal catalytic domain within eIF2B: the guanine-nucleotide exchange factor for translation initiation
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DOI：
10.1093/emboj/cdf515
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发表时间：
2002-10-01
期刊：
影响因子：
11.4
通讯作者：
Pavitt, GD
中科院分区：
文献类型：
--
作者：
Gomez, E;Mohammad, SS;Pavitt, GD
对于真核生物中的蛋白质合成起始，eIF 2B是eIF 2的鸟嘌呤-核苷酸交换因子。eIF 2B是一种重要的多亚基因子，也是酵母和哺乳动物细胞中翻译调控的主要靶标。之前已经表明，最大的eIF 2B亚基eIF 2B是唯一具有催化功能的单一亚基。在这里，我们报告的结果，分子解剖的酵母亚基编码的GCD 6，我们已经确定了催化结构域。通过体外分析一系列N-末端缺失，我们发现最小的催化活性片段包含残基518-712（称为Gcd 6p（518-712））。进一步缺失至位置581（Gcd 6p（581-712））导致核苷酸交换功能丧失，但保留eIF 2结合活性。C端仅缺失61个残基（Gcd 6p（1-651））导致两种功能的丧失。因此，Gcd 6p（518-712）含有两个共同构成eIF 2B催化结构域的区域。最后，我们表明，催化结构域可以提供eIF 2B的生物功能，在体内时，也存在升高水平的eIF 2和tRNA（i）（Met）。
For protein synthesis initiation in eukaryotes, eIF2B is the guanine-nucleotide exchange factor for eIF2. eIF2B is an essential multi-subunit factor and a major target for translational control in both yeast and mammalian cells. It was shown previously that the largest eIF2B subunit, eIF2Bepsilon, is the only single subunit with catalytic function. Here we report the results of a molecular dissection of the yeast a subunit encoded by GCD6 in which we have identified the catalytic domain. By analysis of a series of N-terminal deletions in vitro we find that the smallest catalytically active fragment contains residues 518-712 (termed Gcd6p(518-712)). Further deletion to position 581 (Gcd6p(581-712)) results in loss of nucleotide exchange function, but eIF2-binding activity is retained. C-terminal deletion of only 61 residues (Gcd6p(1-651)) results in loss of both functions. Thus Gcd6p(518-712) contains two regions that together constitute the catalytic domain of eIF2B. Finally, we show that the catalytic domain can provide eIF2B biological function in vivo when elevated levels eIF2 and tRNA(i)(Met) are also present.