Tigerinins: Novel Antimicrobial Peptides from the Indian FrogRana tigerina

Abstract

Four broad-spectrum, 11 and 12 residue, novel antimicrobial peptides have been isolated from the adrenalinestimulated skin secretions of the Indian frog Rana tigerina. Sequences of these peptides have been determined by automated Edman degradation, by mass spectral analysis and confirmed by chemical synthesis. These peptides, which we have named as tigerinins, are characterized by an intramolecular disulfide bridge between two cysteine residues forming a nonapeptide ring. This feature is not found in other amphibian peptides. Conformational analysis indicate that the peptides tend to form ␤-turn structures. The peptides are cationic and exert their activity by permeabilizing bacterial membranes. Tigerinins represent the smallest, nonhelical, cationic antimicrobial peptides from amphibians.Antimicrobial peptides constitute a very important component of the innate immune system in organisms across the evolutionary scale (1-8). Amphibians being the first group of organisms forming a connecting link between land and water are forced to adopt and survive in a variety of conditions laden with pathogenic microbes. Thereby, they are endowed with an excellent chemical defense system composed of pharmacological and antimicrobial peptides (9). Bombinins were the first antimicrobial peptides characterized from the skin of Bombina variegata in 1969 (10). The discovery of magainins from the skin secretions of Xenopus laevis in 1987 (11) triggered extensive search and characterization of antimicrobial peptides from amphibians (12)(13)(14). Antimicrobial peptides from genus Rana share an interesting structural motif composed of a disulfidebridged cationic heptapeptide segment at the COOH-terminal end. Peptides with this motif include brevinins and esculentins which are composed of 24 and 46 amino acids, respectively (14). The primary structures of large number of peptides belonging to this family have been determined. Another group of short peptides composed of 13 residues called temporins, which do not contain this COOH-terminal ring, have also been characterized from frogs of genus Rana (15). However, considering the large variety of amphibian species in nature, antimicrobial peptides from only a small number of them have been characterized, that too only with respect to primary structure. Also, studies directed toward determining structure-function relationships have been confined to magainins (16) and dermaseptins (17, 18). Hence, characterizing host-defense peptides from other species would be of interest and could conceivably result in the identification of new structural motifs which would be useful in designing peptides for therapeutic applications. Rana tigerina is the predominant species of frogs found in India (19). The skin of these frogs have been used traditionally by some tribal communities to heal both open and burn wounds and the antimicrobial components could possibly contribute to the wound healing process (20). In this study, we have described the isolation and characterization of antimicrobial peptides from...

Structure-Function Relationship Studies on the Frog Skin Antimicrobial Peptide Tigerinin 1: Design of Analogs with Improved Activity and Their Action on Clinical Bacterial Isolates

“…Tigerinins have earlier been shown to permeabilize bacterial membranes to N-phenyl-1-N-napthylamine and o-nitrophenyl-␤-D-galactopyranoside (27). It can be reasonably assumed that the activities of the analogs of TGN-1 used in this study also are mediated by membrane permeabilization.…”

“…In contrast to this, only a few nonhelical antimicrobial peptides with a single disulfide bridge, like thanatin and bactenecin, have been used in structurefunction studies (11,25,37,38). We have recently characterized a novel family of short, nonhelical antimicrobial peptides called tigerinins from the skin secretions of the Indian frog Rana tigerina (27). Tigerinins are a unique family of 11-to 12-residue peptides and are characterized by the presence of a stretch of predominantly hydrophobic amino acids with one cationic residue and an amidated C terminus.…”

“…The synthesis and characterization of TGN-1 has been described earlier (27). Other peptides described in this study were synthesized manually on amide crowns (Chiron Technologies) by the solid-phase method using fluorenylmethoxy carbonyl chemistry (2).…”

Novel Bifunctional Inhibitor of Xylanase and Aspartic Protease: Implications for Inhibition of Fungal Growth

“…The first group acts by lysis, which occurs via several mechanisms (34). Lytic peptides may be amphipathic, having two faces, with one being positively charged and the other being neutral and hydrophobic.…”

Antimicrobial peptides from amphibians

“…Recently, an AMP (odorranain V) containing only 9 amino acid residues was identified from the frog O. grahami (24). Tigerinins which contain 11-12 amino acid residues are identified from skin secretions of Indian tiger frog Rana tigerina (53). Some tigerinin-like peptides are also found from the frog Fejervarya cancrivora, which lives in sea water (54).…”