The SV40 Late Protein VP4 Is a Viroporin that Forms Pores to Disrupt Membranes for Viral Release
Figure 6
Activity of VP4 is dependent upon the lipid composition of the membranes.
(A) Membrane disruptive activity of GST-VP4 measured as percentage fluorescence quenching with two sets of LUVs where phosphatidylethanolamine (PE) was excluded from NuM-like LUVs (NuM-Iike-noPE) or the percentage of cholesterol was increased (NuM-Iike+Chol). Each data point shows the average of at least two independent measurements and the error bars denote the standard deviation of the experiment. See Table 1 for lipid fractions. (B) Membrane disruptive activity of GST-VP4 with five different sets of LUVs: PC, Chol+PC, Chol+PC+PE, Chol+PC+PE+SM and Chol+PC+SM. Each data point shows the average of at least two independent measurements and the error bars denote the standard deviation. (C) Flotation of proteins on sucrose gradients after incubation either without (-, lanes 1–3) or with NuM-like-noPE (lanes 4–6), NuM-like (lanes 7–9), or NuM-like+Chol (lanes 10–12) LUVs to separate unbound (U; lanes 2, 5, 8 and 11) and bound (B; lanes 3, 6, 9 and 12) fractions. Proteins were resolved by SDS-PAGE and immunoblotting with anti-GST antibody. (D) Flotation of proteins on sucrose gradients after incubation with PC (lanes 1–3), Chol+PC (lanes 4–6), Chol+PC+PE (lanes 7–9), Chol+PC+PE+SM (lanes 10–12), or Chol+PC+SM (lanes 13–15) LUVs. Proteins were resolved by SDS-PAGE and immunoblotting with anti-GST antibodies.