Roles of yeast eIF2? and eIF2? subunits in the binding of the initiator methionyl-tRNA.

ABSTRACT: Heterotrimeric eukaryotic/archaeal translation initiation factor 2 (e/aIF2) binds initiator methionyl-tRNA and plays a key role in the selection of the start codon on messenger RNA. tRNA binding was extensively studied in the archaeal system. The ? subunit is able to bind tRNA, but the ? subunit is required to reach high affinity whereas the ? subunit has only a minor role. In Saccharomyces cerevisiae however, the available data suggest an opposite scenario with ? having the most important contribution to tRNA-binding affinity. In order to overcome difficulties with purification of the yeast eIF2? subunit, we designed chimeric eIF2 by assembling yeast ? and ? subunits to archaeal ? subunit. We show that the ? subunit of yeast has indeed an important role, with the eukaryote-specific N- and C-terminal domains being necessary to obtain full tRNA-binding affinity. The ? subunit apparently has a modest contribution. However, the positive effect of ? on tRNA binding can be progressively increased upon shortening the acidic C-terminal extension. These results, together with small angle X-ray scattering experiments, support the idea that in yeast eIF2, the tRNA molecule is bound by the ? subunit in a manner similar to that observed in the archaeal aIF2-GDPNP-tRNA complex.

SUBMITTER: Naveau M 

PROVIDER: S-EPMC3553985 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature