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 language | English |
|---|---|
| Pages (from-to) | 9127-9136 |
| Number of pages | 10 |
| Journal | Biochemistry |
| Volume | 42 |
| Issue number | 30 |
| DOIs | |
| Publication status | Published - Aug 5 2003 |
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- Biochemistry
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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 journal › Article
}
TY - JOUR
T1 - Two redox-active β-carotene molecules in photosystem II
AU - Tracewell, Cara A.
AU - Brudvig, Gary W
PY - 2003/8/5
Y1 - 2003/8/5
N2 - 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.
AB - 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.
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U2 - 10.1021/bi0345844
DO - 10.1021/bi0345844
M3 - Article
VL - 42
SP - 9127
EP - 9136
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 30
ER -