Figure 3.

AvrPtoB shows specificity toward group III tomato ubiquitin E2s in in vitro ubiquitination assays. Glutathione S-transferase (GST)-AvrPtoB was tested against purified tomato E2 proteins in in vitro ubiquitination assays to determine the specificity of AvrPtoB toward the E2s. The tomato E2 enzyme used in each reaction is indicated above the lane by its UBC number, and the minus marker (‒) denotes the absence of E2 enzyme in the reaction. AvrPtoB-E2 specificity is confirmed by the presence of a high molecular mass smear of ubiquitinated proteins, detected by the anti-ubiquitin antibody. Polyubiquitinated forms of AvrPtoB were detected by the anti-AvrPtoB antibody. This experiment was repeated two times with similar results. The numbers on the right denote the molecular masses of marker proteins in kD.