Antitoxin component of a type II toxin-antitoxin (TA) system which inhibits the post-segregational killing (PSK) of plasmid-free cells, also referred to as a plasmid addiction system. Binds to and blocks the activity of CcdB; will also remove bound CcdB protein from the CcdB-GyrA complex by forming a CcdA-CcdB complex, a process termed rejuvenation. Functions as a transcriptional corepressor for the ccdAB operon, repression also requires CcdB (By similarity). Homodimer in solution and when bound to DNA. Forms a complex with toxin CcdB; the CcdA-CcdB(2) trimer is sufficient for rejuvenation, whereas maximal operon repression occurs with CcdA(2)CcdB(2) (By similarity). Belongs to the CcdA antitoxin family.