Figure 9.

The Accumulation of Cytochrome b₆ Lacking Assembly Partners Shows a Limited but Noticeable Increase in an FtsH-Defective Context.

(A) Double mutants obtained by crosses of the nuclear ftsh1-1 mutant with chloroplast mutants deleted for either the petA gene, encoding cytochrome f, or the petA and petD genes, the latter encoding subunit IV, accumulated more cytochrome b₆ when cytochrome f was missing than the {ΔpetA} and {ΔpetAD} mutants. Total cell proteins were separated by SDS/urea-PAGE and analyzed by immunodetection with antibodies against cytochrome b₆f subunits (cytochrome f, cytochrome b₆, and subunit IV) and the ATP synthase β-subunit (β CF1) as a loading control.

(B) Unassembled cytochrome f when cytochrome b₆ is missing, as in the {ΔpetB} mutant context, was insensitive to the presence of the ftsh1-1 mutation.