Dose-dependent analysis of VP1-ssDNA binding ability. Increased concentrations of GST-VP1 were incubated with consistent concentrations of minus-strand ssDNA (a) or circular ssDNA (b) to perform dose-dependent analysis. The disappearance of free DNA signals was more obvious when the protein amount increased. Lane M, DNA ladder marker. Bold triangles indicate the protein-DNA complex formed by tested proteins and DNA molecules