Antitoxin HipB - P23873 (HIPB_ECOLI)


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  • Number of PDB entries for P23873: 12
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). UniProt
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Subunit Structure
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). UniProt
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