Background

It is possible to reproduce the active region of a naturally occurring protease inhibitor protein, Bowman Birk Inhibitor, by synthesis of cyclic peptides that encompass the active site of this protein. These peptides retain the structural features of the original protein and most of the inhibitory activity, but are easy to synthesize by automated solid phase methods.

Strategy

The backbone of the Bowman-Birk Inhibitor protein is shown as a ribbon. The molecular structure has a pseudo-two fold symmetry, and two active sites of very similar structure are present per molecule (shown in red). The interaction with the protease involves the formation of a non-covalent complex, shown schematically in the figure. The inhibitor contains many disulphide bridges (yellow), and the active site loop is naturally delimited by one of these disulphides. Synthesis of the loop in isolation (right) generates a short peptide, typically 9-11 residues long, that retains the structural features of this region from the parent protein, and demonstrates inhibitory activity.