Sunflower Trypsin Inhibitor‐1 (SFTI‐1): Sowing Seeds in the Fields of Chemistry and Biology

Abstract Nature‐derived cyclic peptides have proven to be a vast source of inspiration for advancing modern pharmaceutical design and synthetic chemistry. The focus of this Review is sunflower trypsin inhibitor‐1 (SFTI‐1), one of the smallest disulfide‐bridged cyclic peptides found in nature. SFTI‐1 has an unusual biosynthetic pathway that begins with a dual‐purpose albumin precursor and ends with the production of a high‐affinity serine protease inhibitor that rivals other inhibitors much larger in size. Investigations on the molecular basis for SFTI‐1′s rigid structure and adaptable function have planted seeds for thought that have now blossomed in several different fields. Here we survey these applications to highlight the growing potential of SFTI‐1 as a versatile template for engineering inhibitors, a prototypic peptide for studying inhibitory mechanisms, a stable scaffold for grafting bioactive peptides, and a model peptide for evaluating peptidomimetic motifs and platform technologies.