Enables ubiquitin-protein transferase inhibitor activity. Involved in negative regulation of interferon-alpha production. Acts upstream of or within several processes, including cellular response to type II interferon; negative regulation of macromolecule metabolic process; and negative regulation of protein import into nucleus. Predicted to be located in Golgi membrane; nucleus; and perinuclear region of cytoplasm. Predicted to be active in cytoplasmic vesicle. Orthologous to human GBP6 (guanylate binding protein family member 6).