Detergent effect on cytochrome b559 electron paramagnetic resonance signals in the photosystem II reaction centre

The detergent effect on Cytochrome b(559) from spinach photosystem II was studied by electron paramagnetic resonance (EPR) spectroscopy in D1-D2-Cyt b(559) complex preparations. Various n-dodecyl-beta-D-maltoside concentrations from 0 to 0.2% (w/v) were used to stabilise the D1-D2-Cyt b(559) complexes. Low spin heme EPR spectra were obtained but the g. feature positions changed depending on the detergent conditions. Redox potentiometric titrations showed a unique redox potential cytochrome b(559) form (E-m = + 123-150 mV) in all the D1-D2-Cyt b(559) complex preparations indicating that detergent does not affect this property of the protein in those conditions. A similar effect on Cytochrome b(559) 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.