Three Forms of Cytochrome b559 and Their Relation to the Photosynthetic Activity of Chloroplasts

AUTOR(ES)

Wada, Keishiro

RESUMO

Spinach chloroplasts were found to contain three forms of cytochrome b559 that have the same α-peak at 559 nm, but are distinguished from one another by their oxidation-reduction potentials. The high-potential (H) form (Em about 330-350 mV) is reducible by hydroquinone, the middle-potential (M) form (Em about 50-80 mV) is reducible by ascorbate but not by hydroquinone, and the low-potential (L) form is reducible by dithionite but not by ascorbate. The H form was the predominant one in freshly prepared chloroplasts and was strongly correlated with Photosystem II activity. Chloroplast treatments such as aging, sonication, and mild heating, singly or in combination, brought about a shift of the H to the M form. More drastic treatments resulted in shifts of the H and M forms to the L form.

Documentos Relacionados

• Deletion Mutagenesis of the Cytochrome b559 Protein Inactivates the Reaction Center of Photosystem II.
• Targeted mutagenesis of the psbE and psbF genes blocks photosynthetic electron transport: evidence for a functional role of cytochrome b559 in photosystem II.
• A functional model for the role of cytochrome b559 in the protection against donor and acceptor side photoinhibition.
• Site directed mutagenesis of the heme axial ligands of cytochrome b559 affects the stability of the photosystem II complex.
• Structural model of cytochrome b559 in photosystem II based on a mutant with genetically fused subunits