CYTOTOXIC NECROTIZING FACTOR-I FROM ESCHERICHIA-COLI - A TOXIN WITH ANEW INTRACELLULAR ACTIVITY FOR EUKARYOTIC CELLS

Certain pathogenic Escherichia coli strains elaborate a toxin, the cyt otoxic necrotizing factor type 1 (CNF1). CNF1 covalently and specifica lly modifies the p21 Rho GTP-binding protein in mammalian cells by dea midation of the p21 Rho glutamine 63. CNF1 modification of Rho leads t o permanent activation of the GTP-binding protein by blocking intrinsi c and RhoGAP GTPase activities. Rho activation by CNF1 induces reorgan ization of the actin cytoskeleton into large stress fibers and the mul tiplication of focal contact points. Deamidation is a new catalytic ac tivity described for an intracellularly acting toxin.