ISG15/UCRP Protein, Human (C-His)

ISG15/UCRP is a ubiquitin-like protein that plays a pivotal role in the innate immune response to viral infection, either through conjugation to target proteins (ISGylation) or as a free protein. ISGylation involves an enzymatic cascade mediated by E1, E2, and E3 enzymes, leading to the covalent attachment of ISG15 to lysine residues on target proteins such as IFIT1, MX1/MxA, and PPM1B. ISG15 modulates diverse cellular functions via ISGylation, including activation of EIF2AK2/PKR, inhibition of RIGI's antiviral signaling, and enhancement of EIF4E2's translation-suppressive activity. It exhibits broad-spectrum antiviral activity against both DNA and RNA viruses (e.g., influenza A, HIV-1, and Ebola virus) by disrupting viral budding or impairing viral protein functions. The secreted form of ISG15 acts as a cytokine, inducing NK cell proliferation, neutrophil chemotaxis, and ITGAL/ITGB2-mediated activation of SRC family kinases (e.g., LYN, HCK, FGR) to promote IFNG and IL10 secretion, contributing to antimycobacterial immunity.