The binding between p67 and eukaryotic initiation factor 2 plays important roles in the protection of eIF2α from phosphorylation by kinases
The binding between p67 and eukaryotic initiation factor 2 plays important roles in the protection of eIF2α from phosphorylation by kinases
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DOI：
10.1016/j.abb.2006.06.009
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发表时间：
2006-08-15
影响因子：
3.9
通讯作者：
Majumdar, Avijit
中科院分区：
文献类型：
--
作者：
Datta, Bansidhar;Datta, Rekha;Majumdar, Avijit
真核生物起始因子2 α亚基的磷酸化是哺乳动物蛋白质合成起始的主要调控步骤。P67是一种细胞糖蛋白，保护eIF 2 α的磷酸化（来自激酶。先前，我们报道了p67的136/2突变体具有更高水平的eIF 2 α磷酸化（POEP）活性保护。在这项研究中，我们报告说，136/2突变体和它的双突变体含有第二个位点的丙氨酸取代在5个保守的氨基酸残基（13251，D262，H331，E364，和E459）在血清饥饿的大鼠肿瘤肝癌细胞显示增加POEP活性。除D 6/2+H331 A双突变体外，对这些细胞的血清恢复没有消除它们增加的POEP活性。后一种突变体在血清饥饿过程中对POEP活性有轻微的抑制作用，而在血清恢复过程中这种抑制作用显著增强。组成型表达136/2突变体的KRC-7细胞显示PKR磷酸化水平略微降低，ERK 1和2的磷酸化水平显著降低。与野生型p67相比，D 6/2突变体还显示与eIF 2 α和eIF 2 γ的结合增加，与ERK 1和2的结合几乎相似。总之，我们的数据表明，136/2突变体与eIF 2亚基的结合增加可能是其高POEP活性的部分原因。(c)2006年爱思唯尔公司All rights reserved.
Phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 is the major regulatory step in the initiation of protein synthesis in mammals. P67, a cellular glycoprotein, protects phosphorylation of eIF2 alpha( from kinases. Previously, we reported that the 136/2 mutant of p67 has higher levels of protection of eIF2 alpha phosphorylation (POEP) activity. In this study, we report that the 136/2 mutant and its double mutants containing second-site alanine substitutions at the five conserved amino acid residues (13251, D262, H331, E364, and E459) show increased POEP activity in serum-starved rat tumor hepatoma cells. Serum-restoration to those cells did not abolish their increased POEP activity except the D6/2+H331 A double mutant. The latter mutant shows slight inhibition of POEP activity during serum starvation and this inhibition increased significantly during serum restoration. KRC-7 cells constitutively expressing the 136/2 mutant showed slightly decreased levels of PKR phosphorylation and significantly low level of phosphorylation of ERKs 1 and 2. The D6/2 mutant also showed increased binding with eIF2 alpha and eIF2 gamma and almost similar binding with ERKs 1 and 2 as compared to wild type p67. Altogether, our data demonstrate that the increased binding of the 136/2 mutant with the subunits of eIF2 may be in part the cause for its high POEP activity. (c) 2006 Elsevier Inc. All rights reserved.