size, net charge and sequence of the leaders, the group IA lantibiotics can be
further classified into two main groups, i.e. class IA I (nisin) and class IA II
(lacticin 481). The lactocin S N-terminal extension displays no homology with
the class IA I or class IA II leader peptides and may therefore represent a new
class [40].
1.2.2
Small, Heat-Stable, Non-Lanthionine Containing, Membrane-Active Peptides (Class II)
These are less than 10 kDa in size and are characterized by a Gly-Gly –2/–1 Xaa
processing site in the bacteriocin precursor. This site is not restricted to class II
bacteriocins, as it is also present in some lantibiotics [41]. The mature bacteriocins are predicted to form amphiphilic helices with varying amounts of
hydrophobicity, b-sheet structure, and moderate (100 °C) to high (121°C) heat
stability; e.g. pediocin PA-1, lactococcin A, B, and M, leucocin A, sakacin A
(= curvacin A), sakacin P, and lactacin F. Protein engineering of lactococcin B
indicated that its cysteine residue was not necessary for activity [28]. Subgroups
that can be defined within the class II bacteriocins are:
Class (II A) Listeria-active peptides. They have a consensus sequence in the Nterminus of-T-G-N-G-V-X-C-; represented by pediocin PA-1. Other examples
are sakacin A, sakacin P, leucocin A, mesentericin Y105 [42–45].
Class (IIB) Poration complexes consisting of two proteinaceous peptides. These two
peptides are necessary for full activity; examples are lactococcin G, lactococcin M, lactacin F and two-component peptide systems found in the
operon located in the plantaricin A gene cluster [46–49].
Class (IIC) Small, heat-stable, and non-modified bacteriocins translated with sec-dependent leaders. Only two reports have been made up to now; divergicin A
and acidocin B [50, 51].
1.2.3
Large Heat-Labile Proteins (Class III)
These are greater than 30 kDa in size; examples are helveticin J, helveticin V,
acidophilicin A, lactacins A and B [52–56].
A fourth class, proposed by Klaenhammer [21] is rather questionable. This
class comprised the complex bacteriocins, composed of protein plus one or
more chemical moieties (lipid, carbohydrate) required for activity; plantaricin S, leuconocin S, lactocin 27, pediocin SJ-1 [57–61]. The existence of this
fourth class was supported by the observation that some bacteriocin activities
were destroyed by glycolytic and lipolytic enzymes [60]. However, such
bacteriocins have not yet been characterized adequately at the biochemical
level and the recognition of this class therefore seems to be premature. The class
IIC of the Klaenhammer [21] classification has recently been shown not to
exist.
24
E. Sablon et al.
further classified into two main groups, i.e. class IA I (nisin) and class IA II
(lacticin 481). The lactocin S N-terminal extension displays no homology with
the class IA I or class IA II leader peptides and may therefore represent a new
class [40].
1.2.2
Small, Heat-Stable, Non-Lanthionine Containing, Membrane-Active Peptides (Class II)
These are less than 10 kDa in size and are characterized by a Gly-Gly –2/–1 Xaa
processing site in the bacteriocin precursor. This site is not restricted to class II
bacteriocins, as it is also present in some lantibiotics [41]. The mature bacteriocins are predicted to form amphiphilic helices with varying amounts of
hydrophobicity, b-sheet structure, and moderate (100 °C) to high (121°C) heat
stability; e.g. pediocin PA-1, lactococcin A, B, and M, leucocin A, sakacin A
(= curvacin A), sakacin P, and lactacin F. Protein engineering of lactococcin B
indicated that its cysteine residue was not necessary for activity [28]. Subgroups
that can be defined within the class II bacteriocins are:
Class (II A) Listeria-active peptides. They have a consensus sequence in the Nterminus of-T-G-N-G-V-X-C-; represented by pediocin PA-1. Other examples
are sakacin A, sakacin P, leucocin A, mesentericin Y105 [42–45].
Class (IIB) Poration complexes consisting of two proteinaceous peptides. These two
peptides are necessary for full activity; examples are lactococcin G, lactococcin M, lactacin F and two-component peptide systems found in the
operon located in the plantaricin A gene cluster [46–49].
Class (IIC) Small, heat-stable, and non-modified bacteriocins translated with sec-dependent leaders. Only two reports have been made up to now; divergicin A
and acidocin B [50, 51].
1.2.3
Large Heat-Labile Proteins (Class III)
These are greater than 30 kDa in size; examples are helveticin J, helveticin V,
acidophilicin A, lactacins A and B [52–56].
A fourth class, proposed by Klaenhammer [21] is rather questionable. This
class comprised the complex bacteriocins, composed of protein plus one or
more chemical moieties (lipid, carbohydrate) required for activity; plantaricin S, leuconocin S, lactocin 27, pediocin SJ-1 [57–61]. The existence of this
fourth class was supported by the observation that some bacteriocin activities
were destroyed by glycolytic and lipolytic enzymes [60]. However, such
bacteriocins have not yet been characterized adequately at the biochemical
level and the recognition of this class therefore seems to be premature. The class
IIC of the Klaenhammer [21] classification has recently been shown not to
exist.
24
E. Sablon et al.