XENOXINS, A FAMILY OF PEPTIDES FROM DORSAL GLAND SECRETION OF XENOPUS-LAEVIS RELATED TO SNAKE-VENOM CYTOTOXINS AND NEUROTOXINS

Three new, highly similar peptides from the skin secretion of Xenopus laevis have been purified and analyzed by mass spectrometry and Edman degradation. The 66-amino-acid peptides, termed xenoxin-1, -2, and -3, contain 8 cysteines and show similarity to snake venom cytotoxins and short neurotoxins. Assignment of two out of four disulfide bonds sugg ests a tertiary structure similar to that of cytotoxins and short neur otoxins. A cDNA encoding pre-xenoxin-1 was isolated from a X. laevis s kin cDNA library. The nucleotide sequence predicts the synthesis of a precursor with a signal peptide followed by the sequence of the mature peptide. Xenoxin-1 and -2 lack alpha-neuro-toxic activity, have appar ently no antibacterial activity, are low in general toxicity as tested in mice, and have no effect on blood coagulation as measured in a Fac tor VIII procoagulant activity test. Potential functions of xenoxins a s well as evolutionary aspects are discussed.