The precise role of eIF-5A in protein biosynthesis is not known but it functions by promoting the formation of the first peptide bond. Lys-52 undergoes hypusination, a unique post-translational modification that consists in the addition of a butylamino group from spermidine to lysine side chain, leading to the formation of the unusual amino acid hypusine. eIF-5As are the only known proteins to undergo this modification, which is essential for their function. There are at least two genes for eIF-5A in tobacco: 5A1 may regulate the light-dependent translation of specific transcripts while 5A2 may be a housekeeping protein. Belongs to the eIF-5A family.