Bacterial cytolysin that attacks host cell membranes and causes cell rupture by forming a pore (PubMed:25858109, PubMed:30405113). Binds and permeabilizes target cells by forming cation-selective pores (PubMed:25858109). Constitutes the key virulence cytotoxin of K.kingae (PubMed:21248099, PubMed:24664507). Binds cholesterol and oligosaccharides on the surface of host cells (PubMed:30405113). Does not bind beta-2 integrin (ITGB2) on the host cell surface (PubMed:33260488). Myristoylated by RtxC; the toxin only becomes active when modified (PubMed:30405113, PubMed:32461253). Mainly myristoylated; a very minor fraction is acylated with hydroxymyristoyl, lauroyl and palmitoleyl chains fatty acyl groups (PubMed:30405113). Fatty acylation is involved in binding to host membranes and promotes the irreversible insertion of RtxA into the host cell membrane (PubMed:30405113). Cells lacking RtxA display strongly reduced virulence. Belongs to the RTX prokaryotic toxin (TC 1.C.11) family.