A novel immunosuppressory peptide originating from the ubiquitin sequence

► Selected ubiquitin-derived peptides were tested for their immunomodulatory potency. ► Peptide VKTLTGKTI possessed the highest immunosuppressive potency in vitro. ► VKTLTGKTI was also active in allograft survival experiments in mice. ► Basing on ubiquitin crystal structure we designed analogs of selected peptides. ► Immunomodulatory activity of synthesized analogs (cyclic and bivalent) was tested.