Toxic component of a type I toxin-antitoxin (TA) system (Probable). When overexpressed kills cells within minutes; causes collapse of the transmembrane potential and arrest of respiration (PubMed:10361310). Expression leads to membrane depolarization; when protein levels are high enough depolarization probably leads to lowered metabolic activity which in turn induces some cells to enter the persistent state in which they transiently survive antibiotic exposure. Its toxic effect is probably neutralized by antisense antitoxin RNA SokB, which is encoded in trans on the opposite DNA strand (PubMed:10361310). Induced by GTPase Obg expression, which requires alarmone (p)ppGpp. Partial loss of Obg-controlled persistence. Belongs to the Hok/Gef family.