Abstract
The dermaseptins are a family of broad spectrum antimicrobial peptides, 27-34 amino acids long, involved in the defense of the naked skin of frogs against microbial invasion. They are the first vertebrate peptides to show lethal effects against the filamentous fungi responsible for severe opportunistic infections accompanying immunodeficiency syndrome and the use of immunosuppressive agents. A cDNA library was constructed from skin poly(A+) RNA of the arboreal frog Phyllomedusa bicolor and screened with an oligonucleotide probe complementary to the COOH terminus of dermaseptin b. Several clones contained a full-length DNA copy of a 443-nucleotide mRNA that encoded a 78-residue dermaseptin b precursor protein. The deduced precursor contained a putative signal sequence at the NH2 terminus, a 20-residue spacer sequence extremely rich (60%) in glutamic and aspartic acids, and a single copy of a dermaseptin b progenitor sequence at the COOH terminus. One clone contained a complete copy of adenoregulin, a 33-residue peptide reported to enhance the binding of agonists to the A1 adenosine receptor. The mRNAs encoding adenoregulin and dermaseptin b were very similar: 70 and 75% nucleotide identities between the 5'- and 3'-untranslated regions, respectively; 91% amino acid identity between the signal peptides; 82% identity between the acidic spacer sequences; and 38% identity between adenoregulin and dermaseptin b. Because adenoregulin and dermaseptin b have similar precursor designs and antimicrobial spectra, adenoregulin should be considered as a new member of the dermaseptin family and alternatively named dermaseptin b II. Preprodermaseptin b and preproadenoregulin have considerable sequence identities to the precursors encoding the opioid heptapeptides dermorphin, dermenkephalin, and deltorphins. This similarity extended into the 5'-untranslated regions of the mRNAs. These findings suggest that the genes encoding the four preproproteins are all members of the same family despite the fact that they encode end products having very different biological activities. These genes might contain a homologous export exon comprising the 5'-untranslated region, the 22-residue signal peptide, the 20-24-residue acidic spacer, and the basic pair Lys-Arg.
Highlights
The dermaseptins are a family of broad spectrum an- Vertebrate animals must defend themselves against invadtimicrobial peptides, 27-34 amino acids long, involvedin ing microorganisms, which can easilypenetrate theepithelia of the defense of the naked skin of frogs against microbial the respiratory, the gastrointestinal, and the genital systems
A cDNA library was constructed from are endowed with an additional chemical defense system skin poly(A+)RNA of the arborealfrog Phyllomedusa bi- based on a series of broad spectrum antimicrobial peptidesthat color and screened with an oligonucleotide probe are analogous to those found in insects (Bomanand Haltmark, complementary to the COOH terminus of dermaseptin b. 1987; Lehrer et al, 1991)
In an effort to elucidate the mechanism of dermaseptin biosynthesis, we have bred 23 adultspecimens of P. bicolor in the inserts were estimated using the restriction enzyme MluI.5'B-aonthd 3"extremities of the selected specific clones were first sequenced from double-stranded cDNAs (SteDhen et al.. 1990).cDNA inserts were subcloned into M13 mp18 and 19 vectors andcompletely sequenced on laboratorv and obtained a nest of about 2000 eggs from Guay- both DNA strands by the dideoxy method (Sanger et al, 1977)
Summary
Sauuagii, dermaseptin s I, s 11,s 111, s IV, and s V (Mor and Nicolas, 1994);in l? Nicolas, unpublished results) and dermaseptin bI1 (adenoregulin) (Daly et al.,1992)
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