S. moellendorffii BBI3 Is Predicted to Be a BBI Based on Sequence Similarity at the Inhibitory Motifs and Shared Primary Protein Architecture. S. moellendorffii BBI3 Is Predicted to Be a BBI Based on Sequence Similarity at the Inhibitory Motifs and Shared Primary Protein Architecture. (A) Boxshade alignment of S. moellendorffii BBI-like (SmoBBI) protein sequences with soybean BBI (GmaBBIb) and barley BBI (HvuBBIb) shows conservation of the trypsin inhibitory loop (gray box). All proteins, with the exception of SmoBBI4, share a similar protein architecture, with an ER signal (line above sequence) followed by Cys-rich sequence with two spatially distinct conserved inhibitory motifs. Cys residues that are conserved in all sequences are indicated with asterisks. (B) Protein homology model of SmoBBI346-116 aligned with Medicago scutellata BBI (PDB code: 1MVZ) is shown along with the sequence alignment. The conserved inhibitory loops are shown as opaque, while the remaining protein is translucent and the corresponding inhibitory motifs are boxed in the alignment. The side chains of the labeled P1 residues (R64, K67, R90, and L105) and disulfide bonds are displayed in stick format. Amy M. James et al. Plant Cell 2017;29:461-473 ©2017 by American Society of Plant Biologists