Figure 5.

CPK2-GUS, a full-length AtCPK2 protein tagged with GUS, is localized to the ER in transgenic Arabidopsis plants. Fractions from parallel Suc gradients, with and without Mg²⁺, were separated by SDS-PAGE and assayed by immunoblotting with antibodies specific for various membrane markers. AtCPK2-GUS fusion protein was assayed fluorimetrically. Horizontal bars indicate the peak fractions. ▴, +Mg²⁺ gradients; ●, −Mg²⁺ gradients. The fraction with the highest activity was assigned a value of 100% which corresponds to 188 nmol min⁻¹ mL⁻¹ for the +Mg²⁺ gradients and 76 nmol min⁻¹ mL⁻¹ for the −Mg²⁺ gradients. Total GUS activity loaded onto the gradient was 654 nmol min⁻¹ for the +Mg²⁺ gradients and 734 nmol min⁻¹ for the −Mg²⁺ gradients.