The precise role of eIF-5A in protein biosynthesis is not known but it may function as a bimodular protein capable of binding to both RNA and proteins. Involved in xylogenesis. Expressed in leaf vasculature and inflorescence stems. Present in xylem tissue but not in phloem, and in developing vessel members, but not in mature vessels members. Detected in anthers. Increases at the onset of leaf senescence. Up-regulated at post-transcriptional level by iron deficiency. Lys-51 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. No visible phenotype, but presence of extra root protoxylem cell files. Belongs to the eIF-5A family.