Evolutionary relationship between translation initiation factor eIF-2γ and selenocysteine-specific elongation factor SELB: Change of function in translation factors

Abstract

Eubacterial and eukaryotic translation initiation systems have very little in common, and therefore the evolutionary events that gave rise to these two disparate systems are difficult to ascertain. One common feature is the presence of initiation, elongation, and release factors belonging to a large GTPase superfamily. One of these initiation factors, the γ subunit of initiation factor 2 (eIF-2γ), is found only in eukaryotes and archaebacteria. We have sequenced elF-2γ gene fragments from representative diplomonads, parabasalia, and microsporidia and used these new sequences together with new archaebacterial homologues to examine the phylogenetic position of elF-2γ within the GTPase superfam..