Figure 4.

Alkaline extraction of chloroplasts purified from transfected A. thaliana protoplasts. (A) Chloroplasts were isolated from transfected protoplasts that expressed the C-terminal 56- or 100-residues of BsToc159 fused to the C-terminus of EGFP (left and middle panels), or AtOEP7, an integral outer envelope protein, fused to the N-terminus of EGFP (right panel). Purified chloroplasts were incubated in CO²⁻₃ buffer (pH 11.5) or HEPES buffer (pH 7.3) on ice for 10 min. The precipitated membrane pellets were subjected to immunoblot analysis using an anti-EGFP antibody and an antibody against Toc34 as loading controls. (B) The relative resistance of the three EGFP fusion constructs to alkaline extraction as determined by densitometric analysis of the immunoreactive bands. Each value represents the mean of three replicates (± SE).