Cytotoxic necrotising factor family
In molecular biology, the cytotoxic necrotising factor family of proteins includes bacterial cytotoxic necrotising factor proteins and the related dermonecrotic toxin (DNT) from "Bordetella" species. Cytotoxic necrotizing factor 1 (CNF1) is a toxin whose structure from "Escherichia coli" revealed a 4-layer alpha/beta/beta/alpha structure containing mixed beta-sheets. CNF1 is expressed in strains of "E. coli" causing uropathogenic and neonatal meningitis. CNF1 alters host cell actin cytoskeleton and promotes bacterial invasion of the blood–brain barrier endothelial cells. CNF1 belongs to a unique group of large cytotoxins that cause constitutive activation of Rho  guanosine triphosphatases (GTPases), which are key regulators of the actin cytoskeleton . "Bordetella" dermonecrotic toxin (DNT) stimulates the assembly of actin stress fibres and focal adhesions by deamidating or polyaminating Gln63 of the small GTPase Rho. DNT is an A-B toxin composed of an N-terminal receptor-binding (B) domain and a C-terminal enzymatically active (A) domain.