Photoinhibition of carotenoidless reaction centers from Rhodobacter sphaeroides by visible light. Effects on protein structure and electron transport

Júlia Tandori, É. Hideg, László Nagy, P. Maróti, I. Vass

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26 Citations (Scopus)

Abstract

Inhibition of electron transport and damage to the protein subunits by visible light has been studied in isolated reaction centers of the non-sulfur purple bacterium Rhodobacter sphaeroides. Illumination by 1100 μEm-2 s-1 light induced only a slight effect in wild type, carotenoid containing 2.4.1. reaction centers. In contrast, illumination of reaction centers isolated from the carotenoidless R26 strain resulted in the inhibition of charge separation as detected by the loss of the initial amplitude of absorbance change at 430 nm arising from the P+QB- → PQB recombination. In addition to this effect, the L, M and H protein subunits of the R26 reaction center were damaged as shown by their loss on Coomassie stained gels, which was however not accompanied by specific degradation products. Both the loss of photochemical activity and of protein subunits were suppressed in the absence of oxygen. By applying EPR spin trapping with 2,2,6,6-tetramethylpiperidine we could detect light-induced generation of singlet oxygen in the R26, but not in the 2.4.1. reaction centers. Moreover, artificial generation of singlet oxygen; also led to the loss of the L, M and H subunits. Our results provide evidence for the common hypothesis that strong illumination by visible light damages the carotenoidless reaction center via formation of singlet oxygen. This mechanism most likely proceeds through the interaction of the triplet State of reaction center chlorophyll with the ground state triplet oxygen in a similar way as occurs in Photosystem II.

Original languageEnglish
Pages (from-to)175-184
Number of pages10
JournalPhotosynthesis Research
Volume70
Issue number2
DOIs
Publication statusPublished - 2001

Fingerprint

Rhodobacter sphaeroides
Protein Transport
photoinhibition
protein structure
Electron Transport
Singlet Oxygen
electron transfer
singlet oxygen
Protein Subunits
protein subunits
Lighting
lighting
Light
Proteins
Rhodospirillaceae
Oxygen
Spin Trapping
oxygen
Proteobacteria
Photosystem II Protein Complex

Keywords

  • Bacterial reaction center
  • Carotenoids
  • Photoinhibition
  • Protein damage
  • Singlet oxygen

ASJC Scopus subject areas

  • Plant Science

Cite this

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title = "Photoinhibition of carotenoidless reaction centers from Rhodobacter sphaeroides by visible light. Effects on protein structure and electron transport",
abstract = "Inhibition of electron transport and damage to the protein subunits by visible light has been studied in isolated reaction centers of the non-sulfur purple bacterium Rhodobacter sphaeroides. Illumination by 1100 μEm-2 s-1 light induced only a slight effect in wild type, carotenoid containing 2.4.1. reaction centers. In contrast, illumination of reaction centers isolated from the carotenoidless R26 strain resulted in the inhibition of charge separation as detected by the loss of the initial amplitude of absorbance change at 430 nm arising from the P+QB- → PQB recombination. In addition to this effect, the L, M and H protein subunits of the R26 reaction center were damaged as shown by their loss on Coomassie stained gels, which was however not accompanied by specific degradation products. Both the loss of photochemical activity and of protein subunits were suppressed in the absence of oxygen. By applying EPR spin trapping with 2,2,6,6-tetramethylpiperidine we could detect light-induced generation of singlet oxygen in the R26, but not in the 2.4.1. reaction centers. Moreover, artificial generation of singlet oxygen; also led to the loss of the L, M and H subunits. Our results provide evidence for the common hypothesis that strong illumination by visible light damages the carotenoidless reaction center via formation of singlet oxygen. This mechanism most likely proceeds through the interaction of the triplet State of reaction center chlorophyll with the ground state triplet oxygen in a similar way as occurs in Photosystem II.",
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author = "J{\'u}lia Tandori and {\'E}. Hideg and L{\'a}szl{\'o} Nagy and P. Mar{\'o}ti and I. Vass",
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T1 - Photoinhibition of carotenoidless reaction centers from Rhodobacter sphaeroides by visible light. Effects on protein structure and electron transport

AU - Tandori, Júlia

AU - Hideg, É.

AU - Nagy, László

AU - Maróti, P.

AU - Vass, I.

PY - 2001

Y1 - 2001

N2 - Inhibition of electron transport and damage to the protein subunits by visible light has been studied in isolated reaction centers of the non-sulfur purple bacterium Rhodobacter sphaeroides. Illumination by 1100 μEm-2 s-1 light induced only a slight effect in wild type, carotenoid containing 2.4.1. reaction centers. In contrast, illumination of reaction centers isolated from the carotenoidless R26 strain resulted in the inhibition of charge separation as detected by the loss of the initial amplitude of absorbance change at 430 nm arising from the P+QB- → PQB recombination. In addition to this effect, the L, M and H protein subunits of the R26 reaction center were damaged as shown by their loss on Coomassie stained gels, which was however not accompanied by specific degradation products. Both the loss of photochemical activity and of protein subunits were suppressed in the absence of oxygen. By applying EPR spin trapping with 2,2,6,6-tetramethylpiperidine we could detect light-induced generation of singlet oxygen in the R26, but not in the 2.4.1. reaction centers. Moreover, artificial generation of singlet oxygen; also led to the loss of the L, M and H subunits. Our results provide evidence for the common hypothesis that strong illumination by visible light damages the carotenoidless reaction center via formation of singlet oxygen. This mechanism most likely proceeds through the interaction of the triplet State of reaction center chlorophyll with the ground state triplet oxygen in a similar way as occurs in Photosystem II.

AB - Inhibition of electron transport and damage to the protein subunits by visible light has been studied in isolated reaction centers of the non-sulfur purple bacterium Rhodobacter sphaeroides. Illumination by 1100 μEm-2 s-1 light induced only a slight effect in wild type, carotenoid containing 2.4.1. reaction centers. In contrast, illumination of reaction centers isolated from the carotenoidless R26 strain resulted in the inhibition of charge separation as detected by the loss of the initial amplitude of absorbance change at 430 nm arising from the P+QB- → PQB recombination. In addition to this effect, the L, M and H protein subunits of the R26 reaction center were damaged as shown by their loss on Coomassie stained gels, which was however not accompanied by specific degradation products. Both the loss of photochemical activity and of protein subunits were suppressed in the absence of oxygen. By applying EPR spin trapping with 2,2,6,6-tetramethylpiperidine we could detect light-induced generation of singlet oxygen in the R26, but not in the 2.4.1. reaction centers. Moreover, artificial generation of singlet oxygen; also led to the loss of the L, M and H subunits. Our results provide evidence for the common hypothesis that strong illumination by visible light damages the carotenoidless reaction center via formation of singlet oxygen. This mechanism most likely proceeds through the interaction of the triplet State of reaction center chlorophyll with the ground state triplet oxygen in a similar way as occurs in Photosystem II.

KW - Bacterial reaction center

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