Also known as: UCRP

The ubiquitin-like ISG15 is conjugated to intracellular target proteins. This pathway is distinct from that of ubiquitination with different substrate specificities and interactions with ligating enzymes. Pro-ISG15 (165 amino acids) is the inactive precursor of ISG15 (158 amino acids). The precursor is processed at the C-terminus by an ISG15-specific protease UBP43 (also known as USP18). The mature form of ISG15 contains the conserved C-terminal di-glycine residues which are critical in activation and conjugation reactions. This protein can be used as a negative control in ISGylation reactions or as a substrate for UBP43.