Linkage specific Tetra-Ub can also be used to investigate mechanism of binding and recognition by E1 or E2 enzymes, deubiquitinating enzymes, E3 ligases or other proteins that contain ubiquitin-associated domains (UBAs) or ubiquitin-interacting motifs (UIMs). This product is formed with wild-type ubiquitin and linkage-specific enzymes. Tetra-Ub is the minimal unit necessary for recognition by the 26S proteasome and contains structural characteristic (such as repeating hydrophobic patches) not present in di-Ub. This product is made with wild-type human recombinant ubiquitin and linkage-specific enzymes.