A novel C3-like ADP-ribosyltransferase from Staphylococcus aureus modifying RhoE and Rnd3

Clostridium botulinum C3 is the prototype of the family of the C3-like tran sferases that ADP-ribosylate exclusively RhoA, -B and -C, The ADP-ribose at Asn-41 results in functional inactivation of Rho reflected by disaggregati on of the actin cytoskeleton. We report on a new C3-like transferase produc ed by a pathogenic Staphylococcus aureus strain, The transferase designated C3(Stau) was cloned from the genomic DNA, At the amino acid level, C3(Stau ) revealed an identity of 35% to C3 from C. botulinum and Clostridium limos um exoenzyme, respectively, and of 78% to EDIN from S, aureus, In addition to RhoA, which is the target of the other C3-like transferases, C3(Stau) mo dified RhoE and Rnd3. RhoE was ADP-ribosylated at Asn-44, which is equivale nt to Asn-41 of RhoA, RhoE and Rnd3 are members of the Rho subfamily, which are deficient in intrinsic GTPase activity and possess a RhoA antagonistic cell function, The protein substrate specificity found with recombinant Rh o proteins was corroborated by expression of RhoE in Xenopus laevis oocytes showing that RhoE was also modified in vivo by C3(Stau) but not by C3 from C. botulinum. The poor cell accessibility of C3(Stau) was overcome by gene ration of a chimeric toxin recruiting the cell entry machinery of C, botuli num C2 toxin, The chimeric C3(Stau) caused the same morphological and cytos keletal changes as the chimeric C. botulinum C3. C3(Stau) is a new member o f the family of the C3-like transferases but is also the prototype of a sub family of RhoE/Rnd modifying transferases.