The genesis of new proteins and new biosyntheses

SFTl-1 (Sunflower Trypsin Inhibitor 1) was the first protein to be shown to have evolved de novo by genetic expansion within an existing protein. I term this type of de novo protein evolution "neoproteinisation". SFTl-1 emerges from a dual-product protein precursor, PawS1 (Preproalbumin with SFTl-1 ), by proteolytic cleavage to produce the two distinct mature proteins, albumin and SFTl-1. Here, I demonstrate SFTl-1 can emerge from other locations within PawS1 or other proteins. Then, I reveal another family of similarly buried peptides, widespread in flowering plants. This second example suggests neoproteinisation might be an overlooked mechanism for de novo protein evolution.