Fig. 1.

Structural classes of CAPs. Representative structures of the six main classes are shown. a The African clawed frog peptide, magainin, is α-helical (PDB code: 2LSA). b The bovine neutrophil peptide, indolicidin, does not contain β-strands or α-helices [12] (PDB code: 1QXQ). c The porcine leukocyte peptide, protegrin-1 adopts a β-hairpin structure stabilized by two disulfide bonds [13] (PDB code: 1PG1). d The synthetic human θ-defensin, HTD-2, is similar to a β-hairpin but pseudo-cyclized by a third, connecting disulfide bond [14] (PDB code: 2LZI). e The human β-defensin, HBD-2, contains a disulfide-bonded, triple-stranded β-sheet [15] (PDB code: 1FD4). f The ornamental tobacco defensin, NaD1, is comprised of a triple-stranded β-sheet with one α-helix. This pseudocyclic peptide is stabilized by four disulfide bonds [16] (PDB code: 1MR4). Images generated using Pymol [17]