| Type: | Family | Name: | Translation elongation factor IF5A, archaeal |
| Description: | Eukaryotic translation initiation factor 5A (eIF-5A) was previously reported to be involved in the first step of peptide bond formation in translation; however more recent work implicates it as a universally conserved translation elongation factor [].In support of its role as a elongation factor: depletion or inactivation of eIF-5A in the yeast Saccharomyces cerevisiae(Baker's yeast) resulted in the accumulation of polysomes and an increase in ribosomal transit times. Addition of recombinant eIF-5A from yeast, but not a derivative lacking hypusine, enhanced the rate of tripeptide synthesis in vitro. Moreover, inactivation of eIF-5A mimicked the effects of the eEF2 inhibitor sordarin, indicating that eIF-5A might function together with eEF2 to promote ribosomal translocation. eIF-5A is a cofactor for the Rev and Rex transactivator proteins of human immunodeficiency virus-1 and T-cell leukaemia virus I, respectively [, , ]. IF-5A is the sole protein in eukaryotes and archaea to contain the unusual amino acid hypusine (Ne-(4-amino-2-hydroxybutyl)lysine) that is an absolute functional requirement. The first step in the post-translational modification of lysine to hypusine is catalyzed by the enzyme deoxyhypusine synthase, the structure of which has been reported. The archaeal IF-5A proteins have not been studied as comprehensively as their eukaryotic homologues, though the crystal structure of the Pyrobaculum aerophilumprotein has been determined. Unmodified P. aerophilum IF-5A is found to be a beta structure with two domains and three separate hydrophobic cores. The lysine (Lys42) that is post-translationally modified by deoxyhypusine synthase is found at one end of the IF-5A molecule in a turn between beta strands beta4 and beta5; this lysine residue is freely solvent accessible. The C-terminal domain is found to be homologous to the cold-shock protein CspA of E. coli, which has a well characterised RNA-binding fold, suggesting that IF-5A is involved in RNA binding [].This entry represents the archaeal IF-5A proteins. | Short Name: | Transl_elong_IF5A_arc |
