Toxic component of a type I toxin-antitoxin (TA) system. Overexpression causes rapid cell killing, probably by disrupting the cell inner membrane and disruption of ATP synthesis. Expression of the proteinaceous toxin is probably controlled by an antisense sRNA, in this case rdlB. Only a few of these TA systems have been mechanistically characterized; the mechanisms used to control expression of the toxin gene are not necessarily the same (Probable). Belongs to the Ldr toxic peptide family.