Two redox-active β-carotene molecules in photosystem II

Cara A. Tracewell, Gary W Brudvig

Research output: Contribution to journalArticle

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Abstract

Photosystem II (PS II) contains secondary electron-transfer paths involving cytochrome b559 (Cyt b559), chlorophyll (Chl), and β-carotene (Car) that are active under conditions when oxygen evolution is blocked such as in inhibited samples or at low temperature. Intermediates of the secondary electron-transfer pathways of PS II core complexes from Synechocystis PCC 6803 and Synechococcus sp. and spinach PS II membranes have been investigated using low temperature near-IR spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. We present evidence that two spectroscopically distinct redoxactive carotenoids are formed upon low-temperature illumination. The Car+ near-IR absorption peak varies in wavelength and width as a function of illumination temperature. Also, the rate of decay during dark incubation of the Car+ peak varies as a function of wavelength. Factor analysis indicates that there are two spectral forms of Car+ (CarA + has an absorbance maximum of 982 nm, and CarB + has an absorbance maximum of 1027 nm) that decay at different rates. In Synechocystis PS II, we observe a shift of the Car+ peak to shorter wavelength when oxidized tyrosine D (YD .) is present in the sample that is explained by an electrostatic interaction between YD . and a nearby β-carotene that disfavors oxidation of CarB. The sequence of electron-transfer reactions in the secondary electron-transfer pathways of PS II is discussed in terms of a hole-hopping mechanism to attain the equilibrated state of the charge separation at low temperatures.

Original languageEnglish
Pages (from-to)9127-9136
Number of pages10
JournalBiochemistry
Volume42
Issue number30
DOIs
Publication statusPublished - Aug 5 2003

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Photosystem II Protein Complex
Carotenoids
Oxidation-Reduction
Molecules
Temperature
Electrons
Synechocystis
Lighting
Wavelength
Spectrum Analysis
Synechococcus
Spinacia oleracea
Electron Spin Resonance Spectroscopy
Factor analysis
Chlorophyll
Coulomb interactions
Static Electricity
Statistical Factor Analysis
Paramagnetic resonance
Tyrosine

ASJC Scopus subject areas

  • Biochemistry

Cite this

Two redox-active β-carotene molecules in photosystem II. / Tracewell, Cara A.; Brudvig, Gary W.

In: Biochemistry, Vol. 42, No. 30, 05.08.2003, p. 9127-9136.

Research output: Contribution to journalArticle

Tracewell, Cara A. ; Brudvig, Gary W. / Two redox-active β-carotene molecules in photosystem II. In: Biochemistry. 2003 ; Vol. 42, No. 30. pp. 9127-9136.
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