Formation of tyrosine radicals in photosystem II under far-red illumination.

ABSTRACT: Photosystem II (PS II) contains two redox-active tyrosine residues on the donor side at symmetrical positions to the primary donor, P₆₈₀. Tyr_Z, part of the water-oxidizing complex, is a preferential fast electron donor while Tyr_D is a slow auxiliary donor to P₆₈₀⁺. We used PS II membranes from spinach which were depleted of the water oxidation complex (Mn-depleted PS II) to study electron donation from both tyrosines by time-resolved EPR spectroscopy under visible and far-red continuous light and laser flash illumination. Our results show that under both illumination regimes, oxidation of Tyr_D occurs via equilibrium with Tyr_Z^• at pH 4.7 and 6.3. At pH 8.5 direct Tyr_D oxidation by P₆₈₀

SUBMITTER: Ahmadova N 

PROVIDER: S-EPMC5851703 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature