Purification and characterization of human deoxyhypusine synthase from HeLa cells

Post-translational modification of a specific lysine residue in eukaryotic initiation factor 5A is essential for cell viability. The amino acid hypusine, which is the product of this modification, is derived in two subsequent enzyme-catalyzed reactions. We have purified and characterized the enzyme responsible for the first step in hypusine modification, deoxyhypusine synthase, from HeLa cells. The human enzyme is multimeric with a native apparent molecular weight of 150,000 consisting of subunits of 41,000. The amino acid sequences of its peptide fragments share high sequence identity with a hypothetical protein (YHRO68w) on chromosome VIII of Saccharomyces cerevisiae. This protein appears to be the deoxyhypusine synthase of yeast.