A novel heterodimeric antimicrobial peptide from the tree-frog Phyllomedusa distincta

We present here the purification and the analysis of the structural and fun ctional properties of distinctin, a 5.4 kDa heterodimeric peptide with anti microbial activity from the tree-frog Phyllomedusa distincta, This peptide a as isolated from the crude extract of skin granular glands by different c hromatographic steps, Its minimal inhibitory concentration was determined a gainst pathogenic Escherichia coli, Staphlococcus aureus, Enterococcus faec alis and Pseudomonas aeruginosa strains. Amino acid sequencing and mass spe ctrometric investigations demonstrated that distinctin is constituted of tw o different polypeptide chains connected by an intermolecular disulphide br idge. Circular dichroism and Fourier-transformed infrared spectroscopy stud ies showed that this molecule adopts, in water, a structure containing a si gnificant percentage of antiparallel beta -sheet, A conformational variatio n was observed under experimental conditions mimicking a membrane-like envi ronment. Database searches did not show sequence similarities with any know n antimicrobial peptides, In the light of these results, we can consider di stinctin as the first example of a new class of antimicrobial heterodimeric peptides from frog skin. (C) 2001 Federation of European Biochemical Socie ties. Published by Elsevier Science B,V, All rights reserved.