Exploring the antibacterial potential of Lactococcus lactis subsp. lactis bv. diacetylactis BGBU1-4 by genome mining, bacteriocin gene overexpression, and chemical protein synthesis of lactolisterin BU variants

Abstract

Lactic acid bacterium Lactococcus lactis BGBU1-4 produces 43 amino acids (aa) long bacteriocin, lactolisterin BU (LBU), a 5.161 kDa peptide with potent antibacterial activity against many Gram-positive pathogens. In addition, BGBU1-4 produces an additional unknown product of 3.642 kDa with antibacterial activity. Here, we determined that the significant amount of naturally produced LBU breaks down to create a 3.642 kDa truncated form of LBU bacteriocin consisting of 31 N-terminal aa (LBU1-31) that exhibits 12.5% antibacterial activity of the full length LBU. We showed that chemically synthesized LBU is stable and 50% less active than native LBU, and so we used the synthetic peptides of LBU and its variants to further study their activities and antibacterial potential. Deletion analysis of LBU revealed that the 24 N-terminal aa of LBU (LBU1-24) are responsible for antibacterial activity, while downstream aa (25-43) determine the species-specific effectiveness of LBU. Although LBU1-31 contains aa 1-24, the truncation at position 31 is predicted to change the structure within aa 15-31 and might impact on antibacterial activity. Intriguingly, whole genome sequencing and genome mining established that BGBU1-4 is abundant in genes that encode potential antibacterials, but produces LBU and its breakdown product LBU1-31 exclusively.

Heterologously expressed SacP23, a novel bacteriocin from Paenibacillus polymyxa #23, is active against methicillin resistant Staphylococcus aureus

“…This indicates that the peptide is processed further than the simple removal of the predicted amino-terminal leader sequence, either by further trimming at the amino or carboxy termini. A similar finding of unpredicted processing of a bacteriocin has been reported for lactolisterin BU [ 61 ]. Attempts to characterize the amino-terminal end of the peptide were unsuccessful, indicating that there was some form of modification that was resistant to Edman degradation analysis.…”

Design of Novel Saposin-like Bacteriocins Using a Hybrid Approach

“…It could be speculated that these peptides are active when delivered in the cytoplasm of E. coli (e.g, inner membrane perturbation/permeabilization), and that the lack of activity in our screen is due to the outer membrane barrier. A failure to express a similar protein fusion in E. coli was recently reported by Malesevic et al (2023), in this work the authors tried to express a fusion of LliBU (ISP1) to MBP [49]. LliBU is a peptide of similar physicochemical properties as the hybrid peptides.…”