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Redox signalling and the structural basis of regulation of photosynthesis by protein phosphorylation
Author(s) -
Allen J. F.,
Nilsson A.
Publication year - 1997
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1997.tb00012.x
Subject(s) - thylakoid , photosystem ii , photosystem , photosystem i , chloroplast , biophysics , phosphorylation , photosynthesis , dephosphorylation , p700 , light harvesting complexes of green plants , redox , chemistry , photosynthetic reaction centre , protein phosphorylation , biology , biochemistry , protein kinase a , phosphatase , organic chemistry , gene
In photosynthesis in chloroplasts and cyanobacteria, redox control of thylakoid protein phosphorylation regulates distribution of absorbed excitation energy between the two photosystems. When electron transfer through chloroplast photosystem II (PSII) proceeds at a rate higher than that through photosystem I (PSI), chemical reduction of a redox sensor activates a thylakoid protein kinase that catalyses phosphorylation of light‐harvesting complex II (LHCII). Phosphorylation of LHCII increases its affinity for PSI and thus redistributes light‐harvesting chlorophyll to PSI at the expense of PSII. This short‐term redox signalling pathway acts by means of reversible, post‐translational modification of pre‐existing proteins. A long‐term equalisation of the rates of light utilisation by PSI and PSII also occurs: by means of adjustment of the stoichiometry of PSI and PSII. It is likely that the same redox sensor controls both state transitions and photosystem stoichiometry. A specific mechanism for integration of these short‐ and long‐term adaptations is proposed. Recent evidence shows that phosphorylation of LHCII causes a change in its 3‐D structure, which implies that the mechanism of state transitions in chloroplasts involves control of recognition of PSI and PSII by LHCII. The distribution of LHCII between PSII and PSI is therefore determined by the higher relative affinity of phospho‐LHCII for PSI, with lateral movement of the two forms of the LHCII being simply a result of their diffusion within the membrane plane. Phosphorylation‐induced dissociation of LHCII trimers may induce lateral movement of monomeric phospho‐LHCII, which binds preferentially to PSI. After dephosphorylation, monomeric, unphosphorylated LHCII may trimerize at the periphery of PSII.