Mutagenesis of CP43-arginine-357 to serine reveals new evidence for (bi)carbonate functioning in the water oxidizing complex of Photosystem II

Gennady Ananyev, Tuan Nguyen, Cindy Putnam-Evans, G Charles Dismukes

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The chlorophyll-binding protein CP43 is an inner subunit of the Photosystem II (PSII) reaction center core complex of all oxygenic photoautotrophs. X-Ray structural evidence places the guanidinium cation of the conserved arginine 357 residue of CP43 within a few Angstroms to the Mn4Ca cluster of the water-oxidizing complex (WOC) and has been implicated as a possible carbonate binding site. To test the hypothesis, the serine mutant, CP43-R357S, from Synechocystis PCC 6803 was investigated by PSII variable fluorescence (F v/Fm) and simultaneous flash O2 yield measurements in cells and thylakoid membranes. The R357S mutant assembles PSII-WOC centers, but is unable to grow photoautotrophically. Reconstitution of O2 evolution by photoactivation and the occurrence of period-four oscillations of Fv/Fm establishes that the R357S mutant contains an assembled Mn4Ca cluster, but turnover is impaired as seen by an 11-fold larger Kok double miss parameter and faster decay of upper S states. Using pulsed light to avoid photoinactivation, wild-type cells and thylakoid membranes exhibit a 2-4-fold loss in O2 evolution rate upon partial bicarbonate depletion under multiple turnover conditions, while the R357S mutant is unaffected by bicarbonate. Arginine R357 appears to function in binding a (bi)carbonate ion essential to normal catalytic turnover of the WOC. The quantum yield of electron donation from the WOC into PSII increases with decreasing turnover rate in R357S mutant cells and involves an aborted two-flash pathway that is distinct from the classical four-flash pattern. We speculate that an altered photochemical mechanism for O2 production occurs via formation of hydrogen peroxide, by analogy to other treatments that retard the kinetics of proton release into the lumen.

Original languageEnglish
Pages (from-to)991-998
Number of pages8
JournalPhotochemical and Photobiological Sciences
Volume4
Issue number12
DOIs
Publication statusPublished - Dec 2005

Fingerprint

mutagenesis
Mutagenesis
Photosystem II Protein Complex
Carbonates
Serine
Arginine
carbonates
flash
Thylakoids
Water
Bicarbonates
water
cells
Cell Membrane
Chlorophyll Binding Proteins
membranes
Membranes
Synechocystis
lumens
Guanidine

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Cell Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Biophysics

Cite this

Mutagenesis of CP43-arginine-357 to serine reveals new evidence for (bi)carbonate functioning in the water oxidizing complex of Photosystem II. / Ananyev, Gennady; Nguyen, Tuan; Putnam-Evans, Cindy; Dismukes, G Charles.

In: Photochemical and Photobiological Sciences, Vol. 4, No. 12, 12.2005, p. 991-998.

Research output: Contribution to journalArticle

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