Pedullà Nadia, Palermo Rocco, Hasenöhrl David, Bläsi Udo, Cammarano Piero, Londei Paola
Department of Cellular Biotechnology and Hematology, University of Rome La Sapienza Viale Regina Elena 324, 00161 Rome, Italy.
Nucleic Acids Res. 2005 Mar 23;33(6):1804-12. doi: 10.1093/nar/gki321. Print 2005.
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 beta-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.
真核生物翻译起始因子2（eIF2）对于起始tRNA（tRNAi）转运至核糖体起着关键作用。在此，我们报道古菌同源物a/eIF2的功能特性。我们已从嗜热古菌嗜热栖热菌中克隆出编码a/eIF2三个亚基的基因，并在体外检测了纯化重组蛋白的活性。我们证明，由重组多肽重构的三聚体因子具有与其真核同源物相似的特性：它与GTP和Met-tRNAi相互作用，并刺激后者与小核糖体亚基结合。然而，古菌蛋白在某些功能方面与其真核对应物有所不同。与eIF2不同，a/eIF2对GDP和GTP具有相似的亲和力，并且β亚基对tRNAi结合没有贡献。根据类eIF2蛋白的进化史，对完整三聚体及其分离亚基进行了详细分析。
