Pasteurella leukotoxins are exotoxins that attack host leukocytes and especially polymorphonuclear cells, by causing cell rupture. The leukotoxin binds to the host LFA-1 integrin and induces a signaling cascade leading to many biological effects, including tyrosine phosphorylation of the CD18 tail, elevation of the intracellular Ca(2+) and lysis of the host cell (By similarity). This leukotoxin is a major contributor to the pathogenesis of lung injury in ovine pneumonic pasteurellosis. It has also weak hemolytic activity. The transmembrane domains are believed to be involved in pore formation in target cells. The Gly-rich region is probably involved in calcium binding, which is required for target cell-binding and cytolytic activity. The C-terminal domain contains an export signal that is recognized by the ABC transporter complex LktBD. Acylated by LktC. The toxin only becomes active when modified (By similarity). The lktCABD operon has a complex mosaic structure that has been derived by extensive inter- and intraspecies horizontal DNA transfer and intragenic recombination events. Belongs to the RTX prokaryotic toxin (TC 1.C.11) family.