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. Negatively regulates its own expression as well as relieving the export block imposed by high-level synthesis of the LamB-LacZ hybrid protein. Overexpression leads to increased doubling time and also suppresses a htrA (degP) null phenotype. 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. This complex is seen to dimerize in solution. Not essential.