Browne Gareth J, Proud Christopher G
Division of Molecular Physiology, School of Life Sciences, University of Dundee, MSI/WTB Complex, Dundee, UK.
Eur J Biochem. 2002 Nov;269(22):5360-8. doi: 10.1046/j.1432-1033.2002.03290.x.
The elongation phase of mRNA translation is the stage at which the polypeptide is assembled and requires a substantial amount of metabolic energy. Translation elongation in mammals requires a set of nonribosomal proteins called eukaryotic elongation actors or eEFs. Several of these proteins are subject to phosphorylation in mammalian cells, including the factors eEF1A and eEF1B that are involved in recruitment of amino acyl-tRNAs to the ribosome. eEF2, which mediates ribosomal translocation, is also phosphorylated and this inhibits its activity. The kinase acting on eEF2 is an unusual and specific one, whose activity is dependent on calcium ions and calmodulin. Recent work has shown that the activity of eEF2 kinase is regulated by MAP kinase signalling and by the nutrient-sensitive mTOR signalling pathway, which serve to activate eEF2 in response to mitogenic or hormonal stimuli. Conversely, eEF2 is inactivated by phosphorylation in response to stimuli that increase energy demand or reduce its supply. This likely serves to slow down protein synthesis and thus conserve energy under such circumstances.
mRNA翻译的延伸阶段是多肽组装的阶段，需要大量的代谢能量。哺乳动物中的翻译延伸需要一组称为真核延伸因子（eEFs）的非核糖体蛋白。其中几种蛋白质在哺乳动物细胞中会发生磷酸化，包括参与将氨酰tRNA招募到核糖体的eEF1A和eEF1B因子。介导核糖体易位的eEF2也会被磷酸化，这会抑制其活性。作用于eEF2的激酶是一种独特且特异的激酶，其活性依赖于钙离子和钙调蛋白。最近的研究表明，eEF2激酶的活性受MAP激酶信号通路和营养敏感的mTOR信号通路调节，这两条通路在有丝分裂原或激素刺激下可激活eEF2。相反，在能量需求增加或供应减少的刺激下，eEF2会因磷酸化而失活。这可能是为了在这种情况下减缓蛋白质合成从而节省能量。
