This linear ubiquitin fusion protein is resistant to the activity of enzymes (DUB's) that cleave the peptide linkage between adjacent ubiquitin molecules.  Ub is not expressed directly as free Ub, but rather as linear fusions either to itself or to certain ribosomal protein subunits.  These Ub-fusion precursors are proteolyzed by deubiquitinating enzymes (DUB's) at the appropriate junction points to yield active Ub monomers with C-termini ending in GG.  There are likely several intracellular DUB's which perform this essential processing role.  This protein may be useful in analyzing interactions between linear ubiquitin and proteins that contain ubiquitin-associated domains (UBA's) or ubiquitin-interacting motifs (UIM's).