Antitoxin component of a type II toxin-antitoxin (TA) system. Functions as an mRNA interferase antitoxin; overexpression prevents HigB-mediated cessation of cell growth and inhibition of cell proliferation. Probably forms a complex with the mRNA interferase HigB which inhibits the mRNA interferase activity. Induced by amino acid starvation and when translation is blocked. Induction is decreased in the absence of the Lon protease suggesting, by homology to other toxin-antitoxin systems, that Lon may degrade the HigA antitoxin. Transcription is negatively regulated by the cognate locus, probably by this protein. A member of the higB-higA operon. Belongs to the HigA antitoxin family.