Inhibits the expression or activity of extracellular murein hydrolases by interacting, possibly with LrgA, with the holin-like protein CidA. The LrgAB and CidA proteins may affect the proton motive force of the membrane. May be involved in programmed cell death (PCD), possibly triggering PCD in response to antibiotics and environmental stresses. Belongs to the CidB/LrgB family. LrgB subfamily.