Design of bioactive peptides derived from CART sequence isolated from the toadfish Thalassophryne nattereri.

The emergence of bacterial resistance due to the indiscriminate use of antibiotics warrants the need for developing new bioactive agents. In this context, antimicrobial peptides are highly useful for managing resistant microbial strains. In this study, we report the isolation and characterization of peptides obtained from the venom of the toadfish Thalassophryne nattereri. These peptides were active against Gram-positive and Gram-negative bacteria and fungi. The primary amino acid sequences showed similarity to Cocaine and Amphetamine Regulated Transcript peptides, and two peptide analogs-Tn CRT2 and Tn CRT3-were designed using the AMPA algorithm based on these sequences. The analogs were subjected to physicochemical analysis and antimicrobial screening and were biologically active at concentrations ranging from 2.1 to 13 µM. Zeta potential analysis showed that the peptide analogs increased the positive charge on the cell surface of Gram-positive and Gram-negative bacteria. The toxicity of Tn CRT2 and Tn CRT3 were analyzed in vitro using a hemolytic assay and tetrazolium salt reduction in fibroblasts and was found to be significant only at high concentrations (up to 40 µM). These results suggest that this methodological approach is appropriate to design novel antimicrobial peptides to fight bacterial infections and represents a new and promising discovery in fish venom.