Toxin-antitoxin system, antidote protein, HigA <p> Proteins in this entry form a distinct group of helix-turn-helix proteins, which are strictly bacterial and nearly always shorter than 110 amino acids. They include the characterised member HigA, without which the killer protein HigB cannot be cloned. The hig (host inhibition of growth) system is noted to be unusual in that killer protein is encoded by the upstream member of the gene pair.</p>