Antitoxin component of a type IV toxin-antitoxin (TA) system. Antitoxin that counteracts the effect of cognate toxin YpjF (PubMed:28257056). Also counteracts the effect of non-cognate toxins CbtA and YfkI (PubMed:28257056). Expressed in mid-log phase at considerably lower levels than antitoxin relB. Single deletion has no effect on expression of cognate toxin ypjF i.e. the probable operon is not autoregulatory (PubMed:28257056). Single deletion leads to increased biofilm formation, deletion of 3 type IV antitoxin genes (cbeA, yafW, yfjZ) has no effect on cell growth (PubMed:28257056). Encoded in prophage CP4-57. Belongs to the CbeA/YafW/YfjZ antitoxin family.