We identified six beta-defensin and four alpha-defensin genes in the platypus genome, shown in alignment. Alternating text color denotes exons, and the first amino acid of the mature peptide is highlighted in orange. Conserved cysteine residues are highlighted in pink. It can be seen that DEFA4 (boxed) has a cysteine spacing that is intermediate between the alpha- and beta-defensins: Like the alpha-defensins, its first two cysteine residues are separated by one amino acid, but the fourth and fifth residues are separated by six rather than nine amino acids. However, DEFA4 does possess an anionic propiece, the net charge of which counterbalances that of its mature defensin domain, which are clear characteristics of alpha-defensins (Liu and Ganz 1995; Hughes and Yeager 1997).
