The EPR spectrum and orientation of cytochrome b‐563 in the chloroplast thylakoid membrane

The EPR spectrum of cytochrome b‐563 in spinach chloroplasts shows that both hemes of the cytochrome are in a low‐spin state with g z = 3.5. The orientation of the two heme planes is found to be perpendicular to the thylakoid membrane plane in magnetically aligned chloroplasts. This may be relevant for the function of cytochrome b‐563, e.g., in electron transport coupled to proton translocation.