Pediocin‐like antimicrobial peptides (class IIa bacteriocins) and their immunity proteins: biosynthesis, structure, and mode of action

Abstract

Pediocin-like antimicrobial peptides (AMPs) form a group of lactic acid bacteria produced, cationic membrane-permeabilizing peptides with 37 to 48 residues. Upon exposure to membrane-mimicking entities, their hydrophilic, cationic, and highly conserved N-terminal region forms a three-stranded antiparallel beta-sheet supported by a conserved disulfide bridge. This N-terminal beta-sheet region is followed by a central amphiphilic alpha-helix and this in most (if not all) of these peptides is followed by a rather extended C-terminal tail that folds back onto the central alpha-helix, thereby creating a hairpin-like structure in the C-terminal half. There is a flexible hinge between the beta-sheet N-terminal region and the hairpin C-terminal region and one thus obtains two domains that may move relative to each other. The cationic N-terminal beta-sheet domain mediates binding of the pediocin-like AMPs to the target-cell surface through electrostatic interactions, while the more hydrophobic and amphiphilic C-terminal hairpin domain penetrates into the hydrophobic part of the target-cell membrane, thereby mediating leakage through the membrane. The hinge provides the structural flexibility that enables the C-terminal hairpin domain to dip into the hydrophobic part of the membrane. Despite extensive sequence similarities, these AMPs differ markedly in their target-cell specificity, and results obtained with hybrid AMPs indicate that the membrane-penetrating hairpin-like C-terminal domain is the major specificity determinant. Bacteria that produce pediocin-like AMPs also produce a 11-kDa cognate immunity protein that protects the producer. The immunity proteins are well-structured, 4-helix bundle cytosolic proteins. They show a high degree of specificity in that they largely recognize and confer immunity only to their cognate AMP and in some cases to a few AMPs that are closely related to their cognate AMP. The C-terminal half of the immunity proteins contains a domain that is involved in specific recognition of the C-terminal membrane-penetrating specificity-determining hairpin domain of the cognate AMP.

Molecular analysis of the bacteriocin-encoding plasmid pDGL1 from Enterococcus durans and genetic characterization of the durancin GL locus

“…The immunity proteins of pediocin-like bacteriocins have recently been divided into subgroups A, B and C based on sequence similarities (Fimland et al, 2005). The alignment results between DurB and bacteriocin31-im (BacB) (Fig.…”

Bacteriocin as an advanced technology in food industry

“…Its representatives have 37e48 amino acid residues with an N-terminal portion with pleated sheet configuration and a C terminus containing one or two a-helices (Fimland et al, 2005). Pediocin PA-1, which is composed of 44 amino acid residues, isthe only bacteriocin belonging to the subclass IIa that is synthesizednot only by different species, but also by different genera of LAB.…”

Functional and safety aspects of enterococci in dairy foods

“…Production of biogenic amines seems to be unfavorable activity of enterococci in fermented dairy products, because biogenic amines have been associated with a number of food poisoning episodes [82]. It has been observed that the prolifi c growth of enterococci in milk and milk products leads to the formation of signifi cant levels of biogenic amines [4,43,83]. In fact, tyramine is the only relevant biogenic amine produced by enterococci isolated from dairy products [84].…”

“…Enterocins usually belong to the Class II bacteriocins. Enterocins are peptide in nature and are often cationic, amphiphilic, membrane-permeabilizing molecules [3,4]. Bacteriocins may inhibit pathogenic bacteria with a benefi cial impact as protective cultures [3].…”