Cloning and sequencing of the homologues of both the bacterial and eukaryotic initiation factor genes (hIF-2 and heIF-2γ from archaeal Halobacterium halobium
The cloning and sequencing of the genes encoding the translational initiation factors (hIF‐2 and heIF‐2 γ) was performed by screening the halophilic archaeon Halobacterium halobium genomic library with a probe constructed from the peptide IGHVDHGK that is conserved in archaeal GTP‐binding elongation factors. The codon usage by the hIF‐2 and heIF‐2 γ genes showed a preference for triplets ending in G or C. This characteristic is almost identical to that of other H. halobium genes. The translated protein of hIF‐2 and heIF‐2 γ genes is made of 414 and 583 amino acid residues, respectively, and contains the sequence motif for the binding of GTP. The sequence of hIF‐2 shows a strong similarity to the initiation factor IF‐2 from Bacteria whereas heIF‐2 γ shows a strong similarity to the initiation factor eIF‐2 γ from Eucarya.