Detergent effect on Cytochromeb559 electron paramagnetic resonance signals in the photosystem II reaction centre

Abstract

The detergent effect on Cytochrome b₅₅₉ from spinach photosystem II was studied by electron paramagnetic resonance (EPR) spectroscopy in D1–D2–Cyt b₅₅₉ complex preparations. Various n-dodecyl-β-D-maltoside concentrations from 0 to 0.2% (w/v) were used to stabilise the D1–D2–Cyt b₅₅₉ complexes. Low spin heme EPR spectra were obtained but the g_z feature positions changed depending on the detergent conditions. Redox potentiometric titrations showed a unique redox potential cytochrome b₅₅₉ form (E^′_m = +123–150 mV) in all the D1–D2–Cyt b₅₅₉ complex preparations indicating that detergent does not affect this property of the protein in those conditions. A similar effect on Cytochrome b₅₅₉ EPR spectrum was observed in more intact photosystem II preparations independently of their aggregation state. This finding indicates that changes due to detergent could be a common phenomenon in photosystem II complexes. Results are discussed in terms of the environment each detergent provides to the protein.