eIF2B, the guanine nucleotide-exchange factor for eukaryotic initiation factor 2. Sequence conservation between the alpha, beta and delta subunits of eIF2B from mammals and yeast.
eIF2B, the guanine nucleotide-exchange factor for eukaryotic initiation factor 2. Sequence conservation between the alpha, beta and delta subunits of eIF2B from mammals and yeast.
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eIF2B，真核起始因子 2 的鸟嘌呤核苷酸交换因子。来自哺乳动物和酵母的 eIF2B 的 α、β 和 δ 亚基之间的序列保守性。
DOI：
10.1042/bj3180637
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Proud,CG
中科院分区：
文献类型：
--
作者：
Price,NT;Mellor,H;Craddock,BL;Flowers,KM;Kimball,SR;Wilmer,T;Jefferson,LS;Proud,CG
鸟嘌呤核苷酸交换因子eIF 2B介导与翻译起始因子eIF 2结合的GDP交换为GTP。这种交换过程是真核生物中控制翻译起始的关键调节步骤。为了提高我们对eIF 2B的结构、功能和调控的理解，我们获得并测序了编码其所有五个亚基的cDNA物种。本文报道了大鼠eIF 2B β和Δ的基因序列。本文重点研究哺乳动物eIF 2B α、β和Δ亚基之间的序列相似性。早期的研究表明，酿酒酵母中eIF 2B的相应亚基（GCN 3、GCD 7和GCD 2）的氨基酸序列具有相当大的相似性。我们证明，这也是真实的哺乳动物亚基。此外，来自哺乳动物和酵母的eIF 2B α、β和Δ序列，沿着来自秀丽隐杆线虫的推定eIF 2B α亚基和来自粟酒裂殖酵母的eIF 2B Δ的序列的比对表明，所有这些序列的C-末端区域之间的大量残基是相同的或保守的。这种强序列保守性表明这些残基可能具有功能重要性。这方面的影响进行了讨论，根据结果有关的亚基eIF 2B在酵母和哺乳动物的功能。我们的研究结果还表明，大鼠和家兔eIF 2B β和Δ亚基在SDS/PAGE上的迁移率存在明显差异，这不是由于它们的长度不同，而是反映了氨基酸组成的差异。我们还通过北方印迹分析检测了编码eIF 2B α、β、Δ和β亚基的mRNA种类在一系列大鼠组织中的相对表达。正如对编码异源三聚体蛋白亚基的mRNA种类所预期的那样，这些亚基彼此之间的表达水平的比率在所检查的不同大鼠组织之间没有变化（肝脏可能除外）。这代表了对编码eIF 2B不同亚基的mRNA种类的表达水平的首次分析。
The guanine nucleotide-exchange factor eIF2B mediates the exchange of GDP bound to translation initiation factor eIF2 for GTP. This exchange process is a key regulatory step for the control of translation initiation in eukaryotic organisms. To improve our understanding of the structure, function and regulation of eIF2B, we have obtained and sequenced cDNA species encoding all of its five subunits. Here we report the sequences of eIF2Bβ and Δ from rat. This paper focuses on sequence similarities between the α, β and Δ subunits of mammalian eIF2B. Earlier work showed that the amino acid sequences of the corresponding subunits of eIF2B in the yeastSaccharomyces cerevisiae(GCN3, GCD7 and GCD2) exhibit considerable similarity. We demonstrate that this is also true for the mammalian subunits. Moreover, alignment of the eIF2Bα, β and Δ sequences from mammals and yeast, along with the sequence of the putative eIF2Bα subunit fromCaenorhabditis elegansand eIF2BΔ fromSchizosaccharomyces pombeshows that a large number of residues are identical or conserved between the C-terminal regions of all these sequences. This strong sequence conservation points to the likely functional importance of these residues. The implications of this are discussed in the light of results concerning the functions of the subunits of eIF2B in yeast and mammals. Our results also indicate that the large apparent differences in mobility on SDS/PAGE between eIF2Bβ and Δ subunits from rat and rabbit are not due to differences in their lengths but reflect differences in amino acid composition. We have also examined the relative expression of mRNA species encoding the α, β, Δ and ϵ subunits of eIF2B in a range of rat tissues by Northern blot analysis. As might be expected for mRNA species encoding subunits of a heterotrimeric protein, the ratios of expression levels of these subunits to one another did not vary between the different rat tissues examined (with the possible exception of liver). This represents the first analysis of the levels of expression of mRNA species encoding the different subunits of eIF2B.