The ascaphins: a family of antimicrobial peptides from the skin secretions of the most primitive extant frog, Ascaphus truei.
The tailed frog Ascaphus truei occupies a unique position in phylogeny as the most primitive extant anuran and is regarded as the sister taxon to the clade of all other living frogs. Eight structurally related peptides, termed ascaphins 1-8, were isolated from norepinephrine-stimulated skin secretions of A. truei and were shown to possess differential growth inhibitory activity against Escherichia coli and Staphylococcus aureus. Ascaphins 2-7 may be represented by the consensus amino acid sequence GX2DX2KGAAKX3KTVAX2IANX.COOH whereas ascaphin-1 (GFRDVLKGAAKAFVKTVAGHIAN.NH2) and ascaphin-8 (GFKDLLKGAAKALVKTVLF.NH2) contain a C-terminally alpha-amidated residue. The ascaphins show no appreciable structural similarity with other families of antimicrobial peptides from frog skin but display limited sequence identity with the cationic, amphipathic alpha-helical peptides pandinin 1 and opistoporin 1, isolated from the venoms of African scorpions. Ascaphin-8 shows the highest potency against a range of pathogenic microorganisms but has the greatest haemolytic activity. The data indicate that the host defence strategy of using antimicrobial peptides in skin secretions arose early in the evolution of anurans.
Conlon
J Michael
JM
Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, 17666 Al-Ain, United Arab Emirates. jmconlon@uaeu.ac.ae
Sonnevend
Agnes
A
Davidson
Carlos
C
Smith
D David
DD
Nielsen
Per F
PF
D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000145:classification / Q000378:metabolism* / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D007928:Lethal Dose 50; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011898:Ranidae / Q000378:metabolism*; D012867:Skin / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; C527844:ascaphin-8 peptide, Ascaphus truei