The archaeal eIF2 homologue: functional properties of an ancient translation initiation factor
Open Access
- 1 January 2005
- journal article
- research article
- Published by Oxford University Press (OUP) in Nucleic Acids Research
- Vol. 33 (6), 1804-1812
- https://doi.org/10.1093/nar/gki321
Abstract
The eukaryotic translation initiation factor 2 (eIF2) is pivotal for delivery of the initiator tRNA (tRNAi) to the ribosome. Here, we report the functional characterization of the archaeal homologue, a/eIF2. We have cloned the genes encoding the three subunits of a/eIF2 from the thermophilic archaeon Sulfolobus solfataricus , and have assayed the activities of the purified recombinant proteins in vitro . We demonstrate that the trimeric factor reconstituted from the recombinant polypeptides has properties similar to those of its eukaryal homologue: it interacts with GTP and Met-tRNAi, and stimulates binding of the latter to the small ribosomal subunit. However, the archaeal protein differs in some functional aspects from its eukaryal counterpart. In contrast to eIF2, a/eIF2 has similar affinities for GDP and GTP, and the β-subunit does not contribute to tRNAi binding. The detailed analysis of the complete trimer and of its isolated subunits is discussed in light of the evolutionary history of the eIF2-like proteins.Keywords
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