Parvin Abraham, PhD Student
Peptidomic analysis of the skin secreted antibacterial peptides of the frog Clinotarsus curtipes and their structure-function studies
Cationic host defense peptides (HDPs)/antimicrobial peptides (AMPs) which can destroy broad spectrum pathogens were isolated from the skin secretion of the frog Clinotarsus curtipes, endemic to Western Ghats, Kerala, a biodiversity hot spot in India. They are evolutionarily conserved component of the innate immune response, produced as a part of the host defense mechanism. The most active fraction of the crude skin secretion contain seven peptides having high amino acid sequence homology with Brevinin family AMPs. The first six members are named as brevinin1CTcu1- brevinin1CTcu6 and the 7th member is named as brevinin2CTcu1. These peptides are bactericidal in nature and adopted as alpha helical conformation in bacterial membrane mimetic environment. Except B1CTcu1, these peptides are hemolytic at their respective MICs and are capable of permeabilating into the bacterial outer and inner membrane. Though these peptides can induce cytoplasmic membrane depolarisation, bacterial cell death and membrane depolarisation were found to be two independent events. Any change in amino acid residues in the N-terminal of the peptide will seriously affect the antibacterial potency of the peptide and its removal steadily decreases antibacterial potency. The C-terminal cyclisation though provides a higher hydrophobic character to the peptide, showed no influence on its antibacterial potency but it may have a significant role on initial binding with bacterial membrane.