Inhibits the expression or activity of extracellular murein hydrolases by interacting, possibly with LrgA, with the holin-like proteins CidA and/or CidB. The LrgAB and CidAB proteins may affect the proton motive force of the membrane. Increases tolerance to penicillin possibly by inhibiting the formation of the CidAB holin-like complexes within the membrane, thus reducing penicillin-induced lethality. Possibly plays a role in programmed cell death (PCD), triggering PCD in response to penicillin, and possibly other antibiotics, and environmental stresses. Regulated by the two-component system LytR/LytS. Belongs to the CidB/LrgB family. LrgB subfamily.