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Bicarbonate binding and the properties of photosystem II electron acceptors
Author(s) -
Nugent Jonathan H.A.,
Corrie Andrew R.,
Demetriou Christalla,
Evans Michael C.W.,
Lockett Christopher J.
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)81236-5
Subject(s) - bicarbonate , chemistry , semiquinone , photosystem ii , electron acceptor , formate , quinone , electron transfer , photochemistry , inorganic chemistry , stereochemistry , biochemistry , photosynthesis , catalysis , organic chemistry
We have investigated the quinone‐binding region of PS II using exchange reactions to replace key components. Bicarbonate was replaced by formate and Q B by exogenous quinones or herbicide. The effects of these changes were monitored using the ESR signals from the Q A iron‐semiquinone and Fe 3+ non‐haem iron components. We observed that Q B binding caused characteristic changes in the Q − A ESR signal and confirmed that the characteristics of Q − A depend on bicarbonate binding. The non‐haem iron was oxidised only under conditions where bicarbonate was bound. The characteristics of bicarbonate binding were observed in Phormidium laminosum PS II, showing that the bicarbonate effect occurs in cyanobacteria. The results support a hypothesis which gives a central role to bicarbonate in providing the conditions for electron transfer in both cyanobacteria and higher plant PS II. It is suggested that bicarbonate binds at or close to the non‐haem iron and influences the characteristics of Q A , Q B and the non‐haem iron.