Genome wide analysis of the antimicrobial peptides in Python bivittatus and characterization of cathelicidins with potent antimicrobial activity and low cytotoxicity [PublishAheadOfPrint]

In this study, we sought to identify novel antimicrobial peptides (AMPs) in Python bivittatus through bioinformatic analyses of publicly available genome information and experimental validation. In our analysis of the python genome, we identified 29 AMP-related candidate sequences. Of these, we selected five cathelicidin-like sequences and subjected them to further in silico analyses. The results showed that these sequences likely have antimicrobial activity. The sequences were named Pb-CATH1–Pb-CATH5 according to their sequence similarity to previously reported snake cathelicidins. We predicted their molecular structure, and then chemically synthesized the mature peptide for three putative cathelicidins and subjected them to biological activity tests. Interestingly, all three peptides showed potent antimicrobial effects against Gram-negative bacteria, but very weak activity against Gram-positive bacteria. Remarkably, Pb-CATH4 showed potent activity against antibiotic-resistance clinical isolates and also possess very low hemolytic activity and cytotoxicity. Pb-CATH4 also showed considerable serum stability. Electron microscopic analysis indicated that Pb-CATH4 exerts its effects via toroidal pore preformation. Structural comparison of the cathelicidins identified in this study to previously reported ones revealed that these Pb-CATHs are representatives of a new group of reptilian cathelicidins lacking the acidic connecting domain. Furthermore, Pb-CATH4 possesses a completely different mature peptide sequence compared to previously described reptilian cathelicidins. These new AMPs may be candidates for the development of alternatives to or complements of antibiotics to control multi-drug resistant pathogens.

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