Material Data Sheet


Price: $199.00
Catalog #: UL-601


500 µg
Data Sheet: 

Interferon­-stimulated Gene 15 (ISG15), also known as Ubiquitin Cross-­reacting Protein (UCRP), is a Ubiquitin-­like protein that is covalently coupled to target proteins in a process termed ISGylation. It is a 165 amino acid (aa) polypeptide with a predicted molecular weight of 18 kDa. ISG15/UCRP exhibits 66% aa sequence identity with its mouse ortholog.  Structurally, ISG15 consists of two tandem Ubiquitin-­like domains that share a similar 3­-dimensional structure with Ubiquitin and other Ubiquitin-­like modifiers including NEDD8 and SUMO1.  Modification of targets by ISG15 occurs in a stepwise enzymatic process similar to that of Ubiquitin.  Enzymes regulating ISGylation include the activating (E1) enzyme UBE1L, the conjugating (E2) enzyme UBE2L6, and ligases (E3) such as HERC5. Removal of ISG15 is catalyzed by the deconjugating enzyme UBP43/USP18.  Functionally, ISG15 has putative roles in the immune response and tumorigenesis. This is reflected by intracellular ISG15 targets that include Cyclin D1, tumor suppressor p63, IRF3, and a range of viral proteins.  It is induced by type 1 interferons and microbial infection, and knockout mice exhibit an increased sensitivity to infection by some viruses.  ISG15 can also be secreted by cells of the immune system and may act in a cytokine-­like manner.  For instance, it is produced by human granulocytes in response to mycobacterium exposure, and natural killer cells and T cells respond to extracellular ISG15/UCRP with IFN­gamma production.  Further supporting a role in immune function, ISG15 mutations are associated with MSMD, an inherited disorder characterized by increased susceptibility to mycobacterial infection.

Product Information

X mg/ml (X µM) in 50 mM HEPES pH 7.5, 100 mM NaCl, 1 mM DTT,  10% Glycerol (v/v)
17 kDa
> 95% by SDS-PAGE under reducing conditions and visualized by Colloidal Coomassie Blue stain

Use & Storage


Recombinant Human ISG15 can be conjugated to substrate proteins via the subsequent actions of an ISG15-­activating (E1) enzyme, an ISG15-­conjugating (E2) enzyme, and an ISG15 ligase (E3).  Reaction conditions will need to be optimized for each specific application. We recommend an initial ISG15 concentration of 10-100 µM.


Store at -80°C. Avoid multiple freeze/thaw cycles.