Effects of pH and H/D-exchange on Si-state lifetimes and miss parameters of photosystem II in the extremophilic red alga Cyanidioschyzon merolae
(English)Manuscript (preprint) (Other academic)
The extremophilic red alga Cyanidioschyzon merolae (C. merolae) grows in hot springs at very low pH (0.2-4.0) and moderately high temperature (40-56oC). PSII in C. merolae is structurally similar to that of cyanobacteria, but the OEC is protected by the four extrinsic proteins PsbV, PsdU, PsbO and PsbQ’, but the redox potential of QA/QA- is significantly less negative in C. merolae (Em = - 104 mV) than in both T. elongatus (Em = -140 mV) and spinach (Em = - 163 mV). Since this significantly different QA/QA- redox potential is bound to affect the internal redox equilibria, we study here the efficiency of Si state transitions and the stability of the S2, S3 and S0 states as a function of pH and H/D exchange via global analysis of flash-induced oxygen evolution patterns. We demonstrate that despite the highly acidic growing conditions, photosystem II in thylakoids isolated from C. merolae behaves very similar to spinach and T. elongatus. The data indicate that the redox potential of QA/QA- plays only a minor role for the miss parameter and the S-state lifetimes, and strongly support the idea that the S2 → S3 transition is the least efficient step during the oxidation of water to molecular oxygen in photosystem II.
Cyanidioschyzon merolae, H/D exchange, flash induced oxygen evolution pattern (FIOP), global fitting program (GFP), photosystem II (PSII), thylakoid
Research subject Physical Chemistry
IdentifiersURN: urn:nbn:se:umu:diva-111860OAI: oai:DiVA.org:umu-111860DiVA: diva2:873742