The C‐terminal sequences of porcine thrombin are active as antimicrobial peptides

Abstract

The C-terminal sequences of porcine thrombin encode a series of peptides with the characteristics of net positive charge and hydrophobicity, suggesting antimicrobial potential. In this study, we synthesized truncated C-terminal peptides to explore their antimicrobial potency and structure-activity relationship. The results showed that some peptides exerted antimicrobial activity against Gram-positive and Gram-negative bacteria, with selectivity for microbial membranes. The antimicrobial potency of the peptides increased with the extension of chain length. Considering toxicity to red blood cells, the 21-mer peptide T-6 displayed the highest therapeutic index of 43.4, suggesting its higher cell selectivity. Typical α-helical conformations were observed upon binding to a bacteria-mimicking environment. The derivatives tended to interact preferentially with negatively charged vesicles compared to zwitterionic vesicles. Flow cytometry and electron microscopy revealed that the peptides targeted bacterial cell membranes and disrupted cytoplasmic membrane integrity, thereby causing the release of cellular contents leading to cell death. Peptide-membrane interaction experiments provided evidence that the peptides killed bacteria via a membrane-mediating mechanism. In summary, the C-terminal sequence of porcine thrombin has antimicrobial functions.

Antibacterial activity and cytotoxicity of a novel bacteriocin isolated from Pseudomonas sp. strain 166

“…6F, bacteriocin PA166 could permeate the bacterial cell membrane in a dose‐dependent manner. When the cell membrane permeated, the membrane potential dissipated and DiSC3(5) was released, leading to the enhancement of fluorescence (Lv et al ., 2016).…”

“…When the cell membrane permeated, the membrane potential dissipated and DiSC3(5) was released, leading to the enhancement of fluorescence (Lv et al, 2016).…”

Functional Characterization of Porcine NK-Lysin: A Novel Immunomodulator That Regulates Intestinal Inflammatory Response

“…Currently, the NK-lysin has attracted considerable research interest since it has been reported to show a broad-spectrum antimicrobial activity and participate in the regulation of immune functions [ 20 ]. More than 12 kinds of porcine antimicrobial peptides have been found, including porcine thrombin, β-defensin-2, cecropin P1, and NK-lysin, which have broad-spectrum bactericidal effect on many microorganisms [ 32 , 33 ]. Among them, NK-lysin can directly combine the lipid part of lipopolysaccharide, resist various bacteria and fungi, such as E. coli , Bacillus megaterium , Acinetobacter acetate , and even dissolve some tumor cells [ 18 ].…”

High Cell Selectivity and Bactericidal Mechanism of Symmetric Peptides Centered on d-Pro–Gly Pairs

“…DiSC 3 -5, a membrane potential-sensitive fluorescent dye, was used to assess the ability of the peptides to disrupt the cytoplasmic membrane as previously described, [42]. Briefly, E. coli ATCC25922 in the mid-log phase was washed three times and diluted to an OD 600 of 0.05 with 5 mM HEPES buffer (containing 20 mM glucose and 100 mM KCl); then, the mixture of E. coli ATCC25922 and 0.5× MIC to 4× MIC peptides was mixed with diSC 3 -5 (final concentration of 0.4 µM) at 37 • C for 1 h. The fluorescence changes from 0 to 1500 s were recorded at the emission wavelength (λ = 670 nm) and excitation wavelength (λ = 622 nm) (Fluorescence Spectrophotometer, F4500, Hitachi, Tokyo, Japan).…”