Figure 4.

Low pH affects the conformation of the amino terminus of SUS without affecting oligomerization state of the native protein. A, Immunoprecipitation (IP) of native s-SUS was performed at pH 7.5 or pH 5.5 with blank Protein-G beads (PG-only) or with the antibodies listed at the top of the figure. Immunoblots (IB) were performed on the IP pellets with the antibody listed to the right of the figure. The positions of PAGE molecular mass markers are shown in kilodaltons on the left of the figure. B, Sucrose cleavage activity (μmol UDP-Glc min⁻¹ mL⁻¹ × 10⁻³) of native s-SUS resolved by size-exclusion chromatography at pH 6.0 (▪, solid line) or pH 7.5 (○, dashed line). The elution positions of molecular mass standards are shown in kilodaltons (kD) under the graph.