Relationship of promagainin to three other prohormones from the skin of Xenopus laevis: a different perspective.

We observed a striking sequence similarity between precursors for promagainin and procaerulein type I (excluding the caerulein peptide region). Additional comparisons of the promagainin precursor with those of other procaeruleins, proxenopsin, and peptide-Gly-Leu-amide revealed that all possess one or more copies of a structurally similar spacer module, from which an amphiphilic spacer peptide is cleaved. Promagainin yields the magainins, spacer peptides with antimicrobial activity; we suggest other spacer peptides may have similar activity. We propose that the genes for the four kinds of hormones were derived from a common ancestral gene through gene and exon duplications and that the procaerulein and proxenopsin genes are mosaic genes in which the original 3'-ends were replaced by exon shuffling.