Structural analysis of the β-subunit of the translation initiation factor aIF2 from different species: Role of Zn ions

The translation initiation factor aIF2 belongs to the aIF-2-beta/ aIF-5 family which is active in the early steps of protein synthesis by forming a ternary complex with GTP and the initiator tRNA. It is involved in the delivery of Met-tRNAiMet to the 40S ribosomal subunit. The solution structure of the intact β-subunit of aIF2 from Sulfolobus solfataricus has been solved by 1H NMR and results composed of an unfolded N-terminus and a folded core domain with four α-helices and three β-strands. The comparison of this structure with the protein of the same family, that we reported here, suggested that that Zn ions can be useful for the correct folding of the C-terminus portion. Starting from this evidence, here we also report a structural homology calculation. The comparison between the Zn-free and Zn-bound forms suggests a possible structure of the terminal region β-subunit of aIF2 from S. solfataricus in presence of Zn.