Class III The Large 10 kDa Bacteriocins

While the bacteriocins characterized from Gram-positive species are predominantly small (< 10 kDa) peptides, several large antimicrobial proteins have been described at both the biochemical and genetic level. These bacteriocins typically manifest as heat-labile proteins, but one apparent exception is propionicin SM1, a heat-stable inhibitory agent produced by P. jensenii (Miescher et al. 2000). It should be noted, however, that aggregates of small peptides, for example, staphylococcin 1580...

Class I The Lanthionine Containing Lantibiotic Bacteriocins

The term lantibiotic (Schnell et al. 1988 Jung 1991) refers to the diverse array of bacterial antibiotic peptides that contain the non-genetically encoded amino acids lanthionine (Lan) and or 3-methyllanthionine (MeLan), as well as various other highly modified amino acids, commonly including the 2,3-unsaturated amino acids dehydroalanine (Dha) and dehydrobutyrine (Dhb). All of the lantibiotics currently described are thought to be produced as ribo-somally synthesized precursor peptides, which...

Colicin D A Possible Intermediate Between Pyocins and Colicins

The modular design of colicins and pyocins provides flexibility for generating new bacteriocins by recombination mechanisms. As described above, colicin B is a classic example, with colicin D-like translocation and receptor-binding domains and a colicin A Y-like pore-forming domain. Similarly, translocation and DNase domains of pyocins S1 and S2 are homologous whereas their receptor-binding domains have been acquired from different sources. Thus, Fig. 3.8 Nucleotide alignment of regulatory...

Models of Colicin Evolution

Riley and co-workers have extensively studied the evolution of colicins, and it is the result of these efforts that colicins are being recognized as a model system for the evolution of Gram-negative bacteriocins Riley 1993a, 1993b, 1998 Riley et al. 1994, 2000 Tan and Riley 1996, 1997a Riley and Wertz 2002a, 2002b . Two mechanisms - diversifying selection and recombination -have been proposed to explain how these molecules have evolved Tan and Riley 1997b . According to the diversifying...

Evolution of Colicin Killing Domains

Colicin Pyocin Classification

The killing domains are the function modules of colicins which catalyze deleterious changes in the sensitive cell, leading to death. Various killing mechanisms are employed by colicins, as described in the sections above. Sequence data of klebicins, S-type pyocins, alveicins, marcescin and cloacins indicate that CLBs exploit the same killing functions as those used by colicins. Alignments of selected colicin and CLB DNase, rRNase and pore-forming domains are shown in Fig. 3.5. Based on these...