Class II Bacteriocin - Class IIa

Class IIa

One important and well studied class of bacteriocins is the class IIa or pediocin-like bacteriocins produced by lactic acid bacteria. All class IIa bacteriocins are produced by food-associated strains, isolated from a variety of food products of industrial and natural origins, including meat products, dairy products and vegetables. Class IIa bacteriocins are all cationic, display anti-Listeria activity, and kill target cells by permeabilizing the cell membrane.

Class IIa bacteriocins contain between 37 and 48 residues. Based on their primary structures, the peptide chains of class IIa bacteriocins may be divided roughly into two regions: a hydrophilic, cationic and highly conserved N-terminal region, and a less conserved hydrophobic/amphiphilic C-terminal region. The N-terminal region contains the conserved Y-G-N-G-V/L 'pediocin box' motif and two conserved cysteine residues joined by a disulfide bridge. It forms a three-stranded antiparallel beta-sheet supported by the conserved disulfide bridge. This cationic N-terminal beta-sheet domain mediates binding of the class IIa bacteriocin to the target cell membrane. The C-terminal region forms a hairpin-like domain that penetrates into the hydrophobic part of the target cell membrane, thereby mediating leakage through the membrane. The two domains are joined by a hinge, which enables movement of the domains relative to each other.

Some proteins known to belong to the class IIa bacteriocin family are listed below:

• Pediococcus acidilactici pediocin PA-1.
• Leuconostoc mesenteroides mesentericin Y105.
• Carnobacterium piscicola carnobacteriocin B2.
• Lactobacillus sakei sakacin P.
• Enterococcus faecium enterocin A.
• Enterococcus faecium enterocin P.
• Leuconostoc gelidum leucocin A.
• Lactobacillus curvatus curvacin A.
• Listeria innocua listeriocin 743A.