Figure 5.

Model for PawS1 Evolution and the Evolutionary Recurrence of the BBI Inhibitory Motif.

(A) A model proposed for the progressive evolution of the BBI mimicking peptide SFTI-1 from within a standard preproalbumin (PAL) with the key sequence changes shown on the right.

(B) Precursor proteins highlighting the location of the inhibitory loop within the mature BBI (XP_003533609), SFTI-1 and its adjacently matured napin, and the mature ORB peptide from amphibian frog skin (DQ672940). ER denotes the ER signal sequence.

(C) Sequences of SFTI-1, ORB, and four partial BBIs.

(D) Structural overlay of SFTI-1 (1SFI), frog ORB lacking two N-terminal and one C-terminal residues (2O9Q), and a BBI from soybean (1BBI).