The mammalian G protein rhoC is ADP-ribosylated by Clostridium botulinum exoenzyme C3 and affects actin microfilaments in Vero cells.

Clostridium botulinum C3 is a recently discovered exoenzyme that ADP-ribosylates a eukaryotic GTP-binding protein of the ras superfamily. We show now that the bacterially-expressed product of the human rhoC gene is ADP-ribosylated by C3 and corresponds in size, charge and behavior to the dominant C3 substrate of eukaryotic cells. C3 treatment of Vero cells results in the disappearance of microfilaments and in actinomorphic shape changes without any apparent direct effect upon actin. Thus the ADP-ribosylation of a rho protein seems to be responsible for microfilament disassembly and we infer that the unmodified form of a rho protein may be involved in cytoskeletal control.