STATISTICAL APPROACH FOR EVOLUTIONARY RELATIONSHIP OF ALPHA-CONOTOXINS AND MEMBERS OF INSULIN-SUPERFAMILY

Similar conserved structures appear in apparently unrelated protein fa milies. Thus, the superfamily of insulin shows an evolutionary relatio nship with the alpha-conotoxins of marine fish-hunting snails as indic ated by methods of protein comparison. In order to reach statistical s ignificance, the A-chains of different insulins, insulin-like growth f actors, relaxins, insulin related peptides from invertebrates were dra wn for comparison. These data were correlated with sequences from rand omly chosen proteins. The alpha-conotoxins show identity scores up to 37.5% and similarity up to 56.2% toward the members of the insulin-sup erfamily. These scores conform to values achieved by comparing the rel axin and the insulin/IGF-sequences. The data show clearly that the ide ntity and similarity values obtained in the comparison with the insuli ns are significantly higher than the scores of randomly chosen protein primary structures. According to our calculated data, this hormone sy stem regulating metabolism and growth in vertebrates and the mentioned toxin-receptor system share the same evolutionary ancestor. However, this statistical approach has to be substantiated on gene level.