title: Participation of S-S loops in inhibitory activity of peanut protease inhibitor B-III.
abstract: A peanut Bowman-Birk (BBI) type protease inhibitors B-III has two regions, 1 and 2, homologous with each other. Each region contains three S-S loops and a reactive site in its outermost loop. The inhibitor was used to investigate the contribution of the S-S loops of BBI-type inhibitors to their inhibitory activity. Two steps of Edman degradation of the native inhibitor cleaved loop III (the innermost S-S loop) of region 1 of B-III, and the antichymotryptic activity of the first reactive site decreased to about 1/4 of that of native B-III. A third step of Edman degradation split loop II and the inhibitory activity at that site became extremely low (about 1/200 of the original value). These results suggest that protease inhibitor B-III maintains its active conformation by means of the three S-S loops and that the conformation is markedly changed by the splitting of loop II.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid; D007700:Kinetics; D010940:Plant Proteins; D011487:Protein Conformation; D014361:Trypsin Inhibitors / Q000494:pharmacology*
chemical_list: D000596:Amino Acids; D010940:Plant Proteins; D014361:Trypsin Inhibitors; C037954:trypsin-chymotrypsin inhibitor B-III, peanut