非典型结合部位细菌起始因子 3 在大亚基核糖体上。

Non-canonical Binding Site for Bacterial Initiation Factor 3 on the Large Ribosomal Subunit.

机构信息

Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Goettingen 37077, Germany.

出版信息

Cell Rep. 2017 Sep 26;20(13):3113-3122. doi: 10.1016/j.celrep.2017.09.012.

DOI:10.1016/j.celrep.2017.09.012

PMID:28954228

Abstract

Canonical translation initiation in bacteria entails the assembly of the 30S initiation complex (IC), which binds the 50S subunit to form a 70S IC. IF3, a key initiation factor, is recruited to the 30S subunit at an early stage and is displaced from its primary binding site upon subunit joining. We employed four different FRET pairs to monitor IF3 relocation after 50S joining. IF3 moves away from the 30S subunit, IF1 and IF2, but can remain bound to the mature 70S IC. The secondary binding site is located on the 50S subunit in the vicinity of ribosomal protein L33. The interaction between IF3 and the 50S subunit is largely electrostatic with very high rates of IF3 binding and dissociation. The existence of the non-canonical binding site may help explain how IF3 participates in alternative initiation modes performed directly by the 70S ribosomes, such as initiation on leaderless mRNAs or re-initiation.

摘要

原核生物的标准翻译起始需要组装 30S 起始复合物（IC），该复合物将 50S 亚基结合形成 70S IC。IF3 是一种关键的起始因子，在早期被招募到 30S 亚基上，并在亚基结合后从其主要结合位点上置换出来。我们使用了四种不同的 FRET 对来监测 50S 结合后 IF3 的重定位。IF3 远离 30S 亚基、IF1 和 IF2，但仍能与成熟的 70S IC 结合。二级结合位点位于核糖体蛋白 L33 附近的 50S 亚基上。IF3 与 50S 亚基之间的相互作用主要是静电的，IF3 的结合和解离速率非常高。非典型结合位点的存在可能有助于解释 IF3 如何参与由 70S 核糖体直接进行的替代起始模式，例如无 5’端帽子的 mRNA 的起始或重新起始。