Figure 4.

Suc gradient fractionation of membranes from wild-type Columbia plants showing colocalization of AtCPK2 with ER markers. Fractions from parallel gradients, with and without Mg²⁺, were separated by SDS-PAGE and assayed by immunoblotting with antibodies specific for AtCPK2, BiP and ACA2 (ER markers), H⁺-ATPase (plasma membrane marker), Vm23 (vacuolar membrane marker), or PM021 (mitochondrial membrane marker). Horizontal bars indicate the peak fractions. Graphs show chlorophyll absorbance (chloroplast marker) and enzyme assay data for latent UDPase (Golgi marker). ▴, +Mg²⁺ gradients; ●, −Mg²⁺ gradients. The fraction with the highest activity was assigned a value of 100%.