Abstract
β-Carotene has been identified as an intermediate in a secondary electron transfer pathway that oxidizes Chlz and cytochrome b 559 in Photosystem II (PS II) when normal tyrosine oxidation is blocked. To test the redox function of carotenoids in this pathway, we replaced the ζ-carotene desaturase gene (zds) or both the zds and phytoene desaturase (pds) genes of Synechocystis sp. PCC 6803 with the phytoene desaturase gene (crtI) of Rhodobacter capsulatus, producing carotenoids with shorter conjugated π-electron systems and higher reduction potentials than β-carotene. The PS II core complexes of both mutant strains contain approximately the same number of chlorophylls and carotenoids as the wild type but have replaced β-carotene (11 double bonds), with neurosporene (9 conjugated double bonds) and β-zeacarotene (9 conjugated double bonds and 1 β-ionylidene ring). The presence of the ring appears necessary for PS II assembly. Visible and near-infrared spectroscopy were used to examine the light-induced formation of chlorophyll and carotenoid radical cations in the mutant PS II core complexes at temperatures from 20 to 160 K. At 20 K, a carotenoid cation radical is formed having an absorption maximum at 898 nm, an 85 nm blue shift relative to the β-carotene radical cation peak in the WT, and consistent with the formation of the cation radical of a carotenoid with 9 conjugated double bonds. The ratio of Chl+/Car+ is higher in the mutant core complexes, consistent with the higher reduction potential for Car+. As the temperature increases, other carotenoids become accessible to oxidation by P680 +.
| Original language | English |
|---|---|
| Pages (from-to) | 38839-38850 |
| Number of pages | 12 |
| Journal | Journal of Biological Chemistry |
| Volume | 280 |
| Issue number | 46 |
| DOIs | |
| Publication status | Published - 2005 |
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ASJC Scopus subject areas
- Biochemistry
Cite this
Construction and characterization of genetically modified Synechocystis sp. PCC 6803 photosystem II core complexes containing carotenoids with shorter π-conjugation than β-carotene. / Bautista, James A.; Tracewell, Cara A.; Schlodder, Eberhard; Cunningham, Francis X.; Brudvig, Gary W; Diner, Bruce A.
In: Journal of Biological Chemistry, Vol. 280, No. 46, 2005, p. 38839-38850.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Construction and characterization of genetically modified Synechocystis sp. PCC 6803 photosystem II core complexes containing carotenoids with shorter π-conjugation than β-carotene
AU - Bautista, James A.
AU - Tracewell, Cara A.
AU - Schlodder, Eberhard
AU - Cunningham, Francis X.
AU - Brudvig, Gary W
AU - Diner, Bruce A.
PY - 2005
Y1 - 2005
N2 - β-Carotene has been identified as an intermediate in a secondary electron transfer pathway that oxidizes Chlz and cytochrome b 559 in Photosystem II (PS II) when normal tyrosine oxidation is blocked. To test the redox function of carotenoids in this pathway, we replaced the ζ-carotene desaturase gene (zds) or both the zds and phytoene desaturase (pds) genes of Synechocystis sp. PCC 6803 with the phytoene desaturase gene (crtI) of Rhodobacter capsulatus, producing carotenoids with shorter conjugated π-electron systems and higher reduction potentials than β-carotene. The PS II core complexes of both mutant strains contain approximately the same number of chlorophylls and carotenoids as the wild type but have replaced β-carotene (11 double bonds), with neurosporene (9 conjugated double bonds) and β-zeacarotene (9 conjugated double bonds and 1 β-ionylidene ring). The presence of the ring appears necessary for PS II assembly. Visible and near-infrared spectroscopy were used to examine the light-induced formation of chlorophyll and carotenoid radical cations in the mutant PS II core complexes at temperatures from 20 to 160 K. At 20 K, a carotenoid cation radical is formed having an absorption maximum at 898 nm, an 85 nm blue shift relative to the β-carotene radical cation peak in the WT, and consistent with the formation of the cation radical of a carotenoid with 9 conjugated double bonds. The ratio of Chl+/Car+ is higher in the mutant core complexes, consistent with the higher reduction potential for Car+. As the temperature increases, other carotenoids become accessible to oxidation by P680 +.
AB - β-Carotene has been identified as an intermediate in a secondary electron transfer pathway that oxidizes Chlz and cytochrome b 559 in Photosystem II (PS II) when normal tyrosine oxidation is blocked. To test the redox function of carotenoids in this pathway, we replaced the ζ-carotene desaturase gene (zds) or both the zds and phytoene desaturase (pds) genes of Synechocystis sp. PCC 6803 with the phytoene desaturase gene (crtI) of Rhodobacter capsulatus, producing carotenoids with shorter conjugated π-electron systems and higher reduction potentials than β-carotene. The PS II core complexes of both mutant strains contain approximately the same number of chlorophylls and carotenoids as the wild type but have replaced β-carotene (11 double bonds), with neurosporene (9 conjugated double bonds) and β-zeacarotene (9 conjugated double bonds and 1 β-ionylidene ring). The presence of the ring appears necessary for PS II assembly. Visible and near-infrared spectroscopy were used to examine the light-induced formation of chlorophyll and carotenoid radical cations in the mutant PS II core complexes at temperatures from 20 to 160 K. At 20 K, a carotenoid cation radical is formed having an absorption maximum at 898 nm, an 85 nm blue shift relative to the β-carotene radical cation peak in the WT, and consistent with the formation of the cation radical of a carotenoid with 9 conjugated double bonds. The ratio of Chl+/Car+ is higher in the mutant core complexes, consistent with the higher reduction potential for Car+. As the temperature increases, other carotenoids become accessible to oxidation by P680 +.
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U2 - 10.1074/jbc.M504953200
DO - 10.1074/jbc.M504953200
M3 - Article
VL - 280
SP - 38839
EP - 38850
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 46
ER -