Antitoxin component of a type II toxin-antitoxin (TA) system. Neutralizes the toxic effect of cognate toxin HipA (PubMed:20616060). Also neutralizes the toxic effect of non-cognate toxin YjjJ (PubMed:28430938). Binds to operator sites with the consensus sequence 5-'TATCCN(8)GGATA-3' to repress the hipBA operon promoter (PubMed:8021189, PubMed:19150849); binding of HipB(2) to DNA induces a 70 degree bend (PubMed:19150849). This forces HipA dimerization, which blocks HipA's active site and thus its toxic action (PubMed:26222023). May play a role in biofilm formation (PubMed:23329678). Degraded by Lon protease; degradation is inhibited in a HipA-HipB complex and when bound to the operator consensus sequence dsDNA. Homodimer (PubMed:8021189). Binds operator DNA sites in the absence of HipA, inducing a 70 degree bend in consecutive operators and deforming DNA between the operators so that HipB dimers bind on opposite faces of the DNA (PubMed:26222023). Forms a HipA(2)HipB(2) heterotetramer which can interact with a single operator site on DNA, inducing a 70 degree bend (PubMed:19150849). When 2 operators are present each HipB dimer contacts 1 HipA molecule, which are brought together by the DNA bend and dimerize, blocking the HipA active site and inactivating its toxic activity (PubMed:26222023). HipA-HipB-induced bending also distorts the -35 and -10 boxes of the promoter and probably prevents sigma-factor binding, and additionally bound HipB and HipA block RNA polymerase access to the -35 box, thus repressing the operon (PubMed:26222023). This complex also blocks the toxic activity of HipA (PubMed:19150849). Mutations present in allele hipA7 (G22S and D291A) decrease the affinity of HipA for HipB (PubMed:20616060). Degraded by Lon protease in vivo; half-life is 17 minutes in wild-type cells and over 200 minutes in a lon deletion strain. In vitro degradation by Lon is Mg(2+)-ATP-dependent (PubMed:22720069). Cannot be disrupted, suggesting it is a functional antitoxin; no visible phenotype when the hipBA operon is deleted (PubMed:8021189, PubMed:20616060). A hipA or a hipB-hipA operon deletion show decreased biofilm production in the absence of antibiotics (PubMed:23329678).