Figure 6.

Subcellular fractionation of AtVTI1a by step sucrose gradient. Postnuclear membranes of Arabidopsis roots were loaded on a step sucrose gradient. After equilibrium by ultracentrifugation at 100,000 × g for 3 h, 0.5-ml fractions were collected from top (1) to bottom of the gradient (25). Equal volumes of odd-numbered fractions were loaded on an SDS-PAGE gel and immunoblotted with anti-AtVTI1a, anti-AtELP, anti-AtPEP12p, and anti-H⁺PPase antibodies. Blots were analyzed by densitometry, and the percentage of the total marker protein detected in each fraction for AtVTI1a, AtPEP12p, AtELP, and H⁺PPase was plotted in A. The sucrose concentration of each fraction was determined by refractometry and plotted in B.