Influence of amino acid substitution on the antimicrobial activity of bacteriocin lactolisterin BU

Abstract

Introduction: Lactolisterin BU (LBU) is a potent bacteriocin derived from Lactococcuslactis subsp. lactisbv. diacetylactis BGBU1-4. It exhibits antimicrobial properties against Gram-positive food spoilage andfoodborne pathogens. This research aimed to explore the impact of amino acid substitution in LBU onits antimicrobial activity by utilizing in silico prediction of LBU’ssecondary structure and amino acid substitutions.Methods: The secondary structure of LBU was predicted using Phyre2 software. Five variants of LBUwere selected and chemically synthesized, along with unaltered LBU and BHT-B,serving as controls. Peptides were twofold diluted in distilled water, resulting in final concentrations ranging from 1000 µg/mlto 0.5 µg/ml. An agarspot test, employing 5 µl of the dilution, was conducted on three indicatorstrains:Lactococcus lactis BGMN1-596, Listeria monocytogenes ATCC19111, and Staphylococcus aureusATCC25923. The presence of inhibition zones was analyzed after overnight incubation at 37°C (S. aureus)and 30°C (L. lactis and L. monocytogenes).Results: Phyre2 analysis unveiled the presence of two α-helices in LBU’s structure. The majority of LBUvariants displayed altered antimicrobial activity, with some changes being genusspecific, potentially attributable to variances in cell wall composition. Some variants completely lost their activity, underscoring the significance of native amino acids or their physicochemical properties in the correspondingpositions within LBU’s structure. Furthermore, it was confirmed that chemically synthesized LBU effectively retains its antimicrobial activity.Conclusion: Changesin amino acid composition give insight on structure-function relationship of LBU.