Gram-positive lactobacilli produce bacteriocins to kill closely-related competitor species [1]. To protect themselves from the bacteriocidal activity of this molecule they co-express an immunity protein (for discussion of this operon see Bacteriocin_ ...
Gram-positive lactobacilli produce bacteriocins to kill closely-related competitor species [1]. To protect themselves from the bacteriocidal activity of this molecule they co-express an immunity protein (for discussion of this operon see Bacteriocin_IIc Pfam:PF10439). The immunity protein structure is a soluble, cytoplasmic, antiparallel four alpha-helical globular bundle with a fifth, more flexible and more divergent C-terminal helical hair-pin [2]. The C-terminal hair-pin recognises the C-terminus of the producer bacteriocin and this interaction is sufficient to dis-orient the bacteriocin within the membrane and close up the permeabilising pore that on its own the bacteriocin creates [3]. These immunity proteins interact in the same way with other bacteriocins, family Bacteriocin_II, Pfam:PF01721. Since many enterococci can produce more than one bacteriocin it seems likely that the whole operon can be carried on transferable plasmids [4]. This family also includes ImB2 a protein conferring immunity to antimicrobial activity of the type IIa bacteriocin, carnobacteriocin B2 [5].
