GLN-63 OF RHO IS DEAMIDATED BY ESCHERICHIA-COLI CYTOTOXIC NECROTIZINGFACTOR-I

The actin cytoskeleton is regulated by GTP-hydrolysing proteins, the R ho GTPases(1,2), which act as molecular switches in diverse signal-tra nsduction processes(3). Various bacterial toxins can inactivate Rho GT Pases by ADP-ribosylation(1) or glucosylation(4). Previous research ha s identified Rho proteins as putative targets for Escherichia coli cyt otoxic necrotizing factors 1 and 2 (CNF1 and 2)(5,6). These toxins ind uce actin assembly and multinucleation in culture cells. Here we show that treatment of RhoA with CNF1 inhibits the intrinsic GTPase activit y of RhoA and completely blocks GTPase activity stimulated by the Rho- GTPase-activating protein (rhoGAP). Analysis by mass spectrometry and amino-acid sequencing of proteolytic peptides derived from CNF1-treate d RhoA indicate that CNF1 induces deamidation of a glutamine residue a t position 63 (Gln63) to give constitutively active Rho protein.