Posttranslational formation of hypusine in a single major protein occurs generally in growing cells and is associated with activation of lymphocyte growth.
Growing lymphocytes perform a novel chemical modification of a single protein (Hy+: approximately 18 kd, pI approximately 5.1), resulting in the formation of the unusual amino acid, hypusine (N epsilon-[4-amino-2-hydroxybutyl]lysine). This posttranslational event occurs only following activation of lymphocyte growth. Hypusine formation increases at a rate parallel to protein synthesis during the first 24 hr of growth stimulation, beginning before 6 hr of growth. At all times, hypusine is restricted primarily to the single protein, Hy+. In resting cells, the unmodified substrate protein, Hy0, is continuously synthesized and maintained in a steady-state pool of significant size. In several other cell lines, hypusine formation was also observed in a single protein of approximately 18 kd, pI approximately 5.1, indistinguishable electrophoretically from the lymphocyte protein. Thus Hy+ is a ubiquitous protein showing significant conservation among divergent species. Maintenance by resting lymphocytes of a pool of unmodified protein and early activation during growth of the hypusine-forming enzyme system suggest that this posttranslational modification may be of importance to lymphocyte activation.
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D006224:Cricetinae; D007526:Isoelectric Point; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000378:metabolism*; D008239:Lysine / Q000031:analogs & derivatives*; D051379:Mice; D008970:Molecular Weight; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000378:metabolism*
D000596:Amino Acids; D011506:Proteins; C100028:hypusine; D008239:Lysine