Purity ~90% (SDS-PAGE). A proteinase activates the inhibitor by specific proteolysis in the bait region, which, by an unknown mechanism leads to reaction at the cysteinyl-glutamyl internal thiol ester site and to a conformational change, whereby the proteinase is trapped and/or covalently bound to the inhibitor. While in the tetrameric proteinase inhibitors steric inhibition is sufficiently strong, monomeric forms need a covalent linkage between the activated glutamyl residue of the original thiol ester and a terminal amino group of a lysine or another nucleophilic group on the proteinase, for inhibition to be effective. Source: Recombinant protein corresponding to aa700-910 from mouse Mug1, fused to His-Tag at N-terminal, expressed in E. coli. Molecular Weight: ~27kD AA