Uncovering the mechanism of resistance against type III bacteriocin, enterolysin A

摘要

Enterolysin A (EnlA) is a peptidoglycan hydrolase produced by some enterococcal strains with a relatively broad inhibitory spectrum. This enzyme is being classified as a class III bacteriocin (large heat-labile bacteriocin) and it is interesting due to its domain structure resembling the structure of bacteriophage peptidoglycan-degrading enzymes (endolysins). N-terminal catalytic domain is responsible for cleaving chemical bonds in peptidoglycan and C-terminal domain has been thought to be responsible for EnlA binding to its cell wall substrate. Using EnlA C-terminal domain fused with green fluorescent protein (GFP-CWB) followed by fluorescence assay we demonstrated that this part of EnlA represents true cell wall binding (CWB) domain. Although resistance to bacteriocins often results from the expression of so-called "immunity protein" (in bacteriocin producing strain encoded by the same operon as bacteriocin itself), we suppose that in the case of EnlA, resistance results from the absence of specific receptor needed for EnlA binding in resistant strains.