Inhibition of human and yeast 20S proteasome by analogues of trypsin inhibitor SFTI-1.

Starting from the primary structure of sunflower trypsin inhibitor SFTI-1, we designed novel non-covalent inhibitors of human and yeast 20S proteasomes. Peptides with Arg residue in P1 position and two basic amino acid residues (Lys or/and Arg) in P2' and P3' positions strongly inhibited chymotrypsin-like and caspase-like activities, while trypsin-like activity was poorly modified. We found that some SFTI-1 analogues up-regulated exclusively the chymotrypsin-like activity of latent yeast 20S proteasome.