iTRAQ-Based Quantitative Proteomic Analysis of Antibacterial Mechanism of Milk-Derived Peptide BCp12 against Escherichia coli

Abstract

BCp12 is a novel casein-derived antibacterial peptide with a broad-spectrum antibacterial effect. However, its action mechanism against E. coli is unknown. In this study, the growth curve showed that BCp12 had excellent antibacterial activity against E. coli. Red (propidium iodide staining) and green (fluorescein isothiocyanate staining) fluorescence signals were detected at the edges of the E. coli cells treated with BCp12. scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that E. coli cells became rough and shrunken, and part of the cell contents leaked to form a cavity. Furthermore, the iTRAQ proteome analysis showed that 193 and 174 proteins were significantly up-regulated and down-regulated, respectively, after BCp12 treatment. Four enzymes involved in fatty acid degradation of E. coli were down-regulated, disrupting the synthesis of cell membranes. Molecular docking and gel retardation assays showed that BCp12 could bind to genes encoding four key enzymes involved in the fatty acid degradation pathway through hydrogen bonding and hydrophobic interactions, thus significantly inhibiting their activities. Overall, the results indicate that BCp12 inhibits the growth of E. coli, causing metabolic disorders, thus destroying the structure of cell membranes.

Antibacterial Peptides derived from Capra hircus Goat Milk Casein

“…[28] BCp12 was reported through different mechanisms in inhibiting Gram-positive and Gramnegative bacteria, including E. coli growth through membrane cell disruption. [29] Peptide also inhibited growth by alternating lysin malonylation levels in the arginine synthesis pathway, which was influenced by the acyltransferase enzyme. [30] Antibacterial activity of synthetic peptides from pH 6 fraction All detected peptides were synthesized to determine the activity by disc diffusion method against S. aureus and E. coli.…”

“…[30] Although demonstrated by an intracellular mechanism in S. aureus, BCp12 inhibited E. coli growth by membrane cell bacteria disruption. [29] In future investigations, mechanism of action studies by in vitro methods are recommended to determine P4 and other peptides.…”

Recent Advances on Antimicrobial Peptides from Milk: Molecular Properties, Mechanisms, and Applications

“…This is because the cell walls of Gram-negative bacteria possess an outer membrane composed of LPS, phospholipids, lipoproteins, and proteins besides the cytoplasmic membrane. 66 When studying the casein-derived AMP BCp12, Yang et al 67 recognized that the peptide could disrupt the integrity of E. coli cell membranes, thus leak some cell contents and form a cavity to inhibit the growth of E. coli. In addition, a polymeric lipoprotein (OprI), has been identified from the outer membrane of Pseudomonas aeruginosa (P. aeruginosa) and found to be a receptor for helical cationic AMPs.…”