Unbehaun Anett, Marintchev Assen, Lomakin Ivan B, Didenko Tatyana, Wagner Gerhard, Hellen Christopher U T, Pestova Tatyana V
Department of Microbiology and Immunology, SUNY Downstate Medical Center, Brooklyn, NY, USA.
EMBO J. 2007 Jul 11;26(13):3109-23. doi: 10.1038/sj.emboj.7601751. Epub 2007 Jun 14.
Eukaryotic translation initiation factor eIF5B is a ribosome-dependent GTPase that mediates displacement of initiation factors from the 40S ribosomal subunit in 48S initiation complexes and joining of 40S and 60S subunits. Here, we determined eIF5B's position on 80S ribosomes by directed hydroxyl radical cleavage. In the resulting model, eIF5B is located in the intersubunit cleft of the 80S ribosome: domain 1 is positioned near the GTPase activating center of the 60S subunit, domain 2 interacts with the 40S subunit (helices 3, 5 and the base of helix 15 of 18S rRNA and ribosomal protein (rp) rpS23), domain 3 is sandwiched between subunits and directly contacts several ribosomal elements including Helix 95 of 28S rRNA and helix 44 of 18S rRNA, domain 4 is near the peptidyl-transferase center and its helical subdomain contacts rpL10E. The cleavage data also indicate that binding of eIF5B might induce conformational changes in both subunits, with ribosomal segments wrapping around the factor. Some of these changes could also occur upon binding of other translational GTPases, and may contribute to factor recognition.
真核生物翻译起始因子eIF5B是一种核糖体依赖性GTP酶，它介导起始因子从48S起始复合物中的40S核糖体亚基上位移，并介导40S和60S亚基的结合。在此，我们通过定向羟基自由基切割确定了eIF5B在80S核糖体上的位置。在所得模型中，eIF5B位于80S核糖体的亚基间裂隙中：结构域1位于60S亚基的GTP酶激活中心附近，结构域2与40S亚基相互作用（18S rRNA的螺旋3、5和螺旋15的基部以及核糖体蛋白（rp）rpS23），结构域3夹在亚基之间，并直接接触包括28S rRNA的螺旋95和18S rRNA的螺旋44在内的几个核糖体元件，结构域4靠近肽基转移酶中心，其螺旋亚结构域与rpL10E接触。切割数据还表明，eIF5B的结合可能会诱导两个亚基的构象变化，核糖体片段围绕该因子缠绕。其中一些变化也可能在其他翻译GTP酶结合时发生，并可能有助于因子识别。
