Transferase-deficient neurotrophic fragment of clostridial C3 protein. Promotes axonal and dendritic growth and branching of hippocampal neurons at submicromolar concentrations. Also promotes reinnervation of target tissues in organotypical hippocampal/entorhinal slice cultures. Reduces levels of active neuronal RhoA by a non-enzymatic mechanism. Enhances functional recovery and regeneration in a mouse model of spinal cord injury.