Expression and Purification of C-Terminal Region of PI31 Protein to Inhibit 20S Proteasome Activity

PI31 protein, a proteasome inhibitor, is 271 amino acid residues long and contains N-terminal globular and C-terminal proline-rich domains. Proteasome-inhibiting activity is associated with the C-terminal region of PI31. The sequence of the C-terminal region of the PSMF1 gene encoding PI31 protein (151–271 aa) fused at the N-terminus with a six-histidine sequence was constructed. The recombinant C-terminal region of PI31 (6His-cPI31) was expressed in Escherichia coli and purified by metal chelate chromatography. The recombinant 6His-cPI31 protein inhibited in vitro chymotrypsin-like activity of of 20S, but not 26S proteasome.