Class II bacteriocin
Encyclopedia
Class II bacteriocins are a class of small peptide
s that inhibit the growth of various bacteria.
Many Gram-positive bacteria produce ribosomally synthesized antimicrobial peptides
, termed bacteriocin
s.
Bacteriocins for which disulfide bond
s are the only modification to the peptide are Class II bacteriocins.
s 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:
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
s that inhibit the growth of various bacteria.
Many Gram-positive bacteria produce ribosomally synthesized antimicrobial peptides
Antimicrobial peptides
Antimicrobial peptides are an evolutionarily conserved component of the innate immune response and are found among all classes of life. Fundamental differences exist between prokaryotic and eukaryotic cells that may represent targets for antimicrobial peptides...
, termed bacteriocin
Bacteriocin
Bacteriocins are proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain. They are typically considered to be narrow spectrum antibiotics, though this has been debated...
s.
Bacteriocins for which disulfide bond
Disulfide bond
In chemistry, a disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore R-S-S-R. The terminology is widely used in biochemistry...
s are the only modification to the peptide are Class II bacteriocins.
Class IIa
One important and well studied class of bacteriocinBacteriocin
Bacteriocins are proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain. They are typically considered to be narrow spectrum antibiotics, though this has been debated...
s is the class IIa or pediocin-like bacteriocins produced by lactic acid bacteria
Lactic acid bacteria
The lactic acid bacteria comprise a clade of Gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and lactic products, produce...
. 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
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
.
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
Cysteine
Cysteine is an α-amino acid with the chemical formula HO2CCHCH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is polar and thus cysteine is usually classified as a hydrophilic amino acid...
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 acidilacticiPediococcus acidilacticiPediococcus acidilactici is a species of gram positive coccus that is often found in pairs or tetrads. Pediococcus acidilactici is a homo-fermentative bacterium that can grow in a wide range of pH, temperature and osmotic pressure, therefore being able to colonize the digestive tract...
pediocin PA-1. - Leuconostoc mesenteroidesLeuconostoc mesenteroidesLeuconostoc mesenteroides is a species of bacteria sometimes associated with fermentation, under conditions of salinity and low temperatures.-External links:*...
mesentericin Y105. - Carnobacterium piscicola carnobacteriocin B2.
- Lactobacillus sakei sakacin P.
- Enterococcus faeciumEnterococcus faeciumEnterococcus faecium is a Gram-positive, alpha hemolytic or nonhemolytic bacterium in the genus Enterococcus. It can be commensal in the human intestine, but it may also be pathogenic, causing diseases such as neonatal meningitis.Vancomycin-resistant E. faecium is often referred to as VRE.Some...
enterocin A. - Enterococcus faeciumEnterococcus faeciumEnterococcus faecium is a Gram-positive, alpha hemolytic or nonhemolytic bacterium in the genus Enterococcus. It can be commensal in the human intestine, but it may also be pathogenic, causing diseases such as neonatal meningitis.Vancomycin-resistant E. faecium is often referred to as VRE.Some...
enterocin P. - Leuconostoc gelidum leucocin A.
- Lactobacillus curvatus curvacin A.
- Listeria innocua listeriocin 743A.
Class IIb
The class IIb bacteriocins (two-peptide bacteriocins) require two different peptides for activity.Class IIc
Other class II bacteriocins can be grouped together as Class IIc (circular bacteriocins). These have a wide range of effects on membrane permeability, cell wall formation and pheromone actions of target cells.Further reading
- [1]. Sequence and structural relationships of leucocins A-, B- and C-TA33a from Leuconostoc mesenteroides TA33a. Papathanasopoulos MA, Dykes GA, Revol-Junelles AM, Delfour A, von Holy A, Hastings JW; Microbiology 1998;144:1343-1348.
- [2]. Three-dimensional structure of leucocin A in trifluoroethanol and dodecylphosphocholine micelles: spatial location of residues critical for biological activity in type IIa bacteriocins from lactic acid bacteria. Fregeau Gallagher NL, Sailer M, Niemczura WP, Nakashima TT, Stiles ME, Vederas JC; Biochemistry 1997;36:15062-15072.