Structure of archaeal translational initiation factor 2 βγ-GDP reveals significant conformational change of the β-subunit and switch 1 region
Structure of archaeal translational initiation factor 2 βγ-GDP reveals significant conformational change of the β-subunit and switch 1 region
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DOI：
10.1073/pnas.0604165103
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发表时间：
2006-08-29
影响因子：
11.1
通讯作者：
Tanaka, Isao
中科院分区：
文献类型：
--
作者：
Sokabe, Masaaki;Yaot, Min;Tanaka, Isao
Archaeal/eukaryotic initiation factor 2 (a/elF2) consists of alpha-, beta-, and gamma-subunits and delivers initiator methionine tRNA (Met-tRNA(i)) to a small ribosomal subunit in a GTP-dependent manner. The structures of the alF2 beta gamma (archaeal initiation factor 2 beta gamma) heterodimeric complex in the apo and GDP forms were analyzed at 2.8-and 3.4-angstrom resolution, respectively. The results showed that the N-terminal helix and the central helix-turn-helix domain of the beta-subunit bind to the G domain of the gamma-subunit but are distant from domains 2 and 3, to which the alpha-subunit and Met-tRNA(i) bind. This result is consistent with most of the previous analyses of eukaryotic factors, and thus indicates that the binding mode is essentially conserved among a/elF2. Comparison with the uncomplexed structure showed significant differences between the two forms of the beta-subunit, particularly the C-terminal zinc-binding domain, which does not interact with the gamma-subunit and was suggested previously to be involved in GTP hydrolysis. Furthermore, the switch 1 region in the gamma-subunit, which is shown to be responsible for Met-tRNA(i) binding by mutational analysis, is moved away from the nucleotide through the interaction with highly conserved R87 in the beta-subunit. These results implicate that conformational change of the beta-subunit facilitates GTP hydrolysis by inducing the conformational change of the switch 1 region toward the off state.
