Antitoxin component of a type II toxin-antitoxin (TA) system. Labile antitoxin that binds to the YhaV toxin and neutralizes its ribonuclease activity. Also acts as a transcription factor. The YhaV/PrlF complex binds the prlF-yhaV operon, probably negatively regulating its expression (By similarity). Homodimer; forms a complex with YhaV with stoichiometry PrlF(2)-YhaV(4), possibly as a YhaV(2)-PrlF(2)-YhaV(2) complex like the MazFE complex. Deletion of the prlF-yhaV operon has no effect on virulence in mouse infection; the disrupted strain is as virulent as wild-type.