Antitoxin component of a type II toxin-antitoxin (TA) system. Functions as an mRNA interferase antitoxin; overexpression prevents HicA-mediated cessation of cell growth and inhibition of cell proliferation. Probably forms a complex with the mRNA interferase HicA; when the 2 dissociate the mRNA interferase becomes active. Induced by amino acid starvation, carbon starvation and when translation is blocked. Induction no longer occurs in the absence of Lon protease suggesting, by homology to other toxin-antitoxin systems, that Lon may degrade the HicB antitoxin. A member of the hicA-hicB operon. May be degraded by Lon protease. Disruption suppresses an rpoE disruption; in a wild-type background disruption down-regulates extracytoplasmic stress responses and outer membrane vesicle production. Belongs to the HicB antitoxin family. Extended N-terminus.