The ubiquity of the insulin superfamily across the eukaryotes detected using a bioinformatics approach.

The insulin superfamily is composed of a diverse group of proteins that share a common structural design whose most notable feature is a set of disulfide bonds. There is now sufficient experimental and bioinformatics evidence that it is represented in at least a number of well-investigated invertebrates, where they have been found to intervene mainly in complex processes such as mitosis, cell growth, castes differentiation, and fertility. In this article we automated a methodology first proposed elsewhere-that combines sequence similarity with assessing membership to the superfamily by conservation of structuraly key residues-to identify putative insulin-like peptides (ILPs) in completely sequenced genomes, and applied it as a pipeline to a group of 46 organisms both vertebrates and invertebrates. As a result, we were able to identify 1,653 putative members of the insulin superfamily, from 17 putative members in C. savigny to 58 in X. tropicalis. Moreover, we found that structural distinctions-such as peptides length-between functionally diverse members of the superfamily found in vertebrates, that is, insulins, IGFs, and relaxins, are not equally represented in invertebrates genomes, suggesting that such divergence has occurred only recently in the evolutionary history of vertebrates.