Resistance of reaction centers from Rhodobacter sphaeroides against UV-B radiation. Effects on protein structure and electron transport

Júlia Tandori, Z. Máté, P. Maróti, I. Vass

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9 Citations (Scopus)

Abstract

Inhibition of electron transport and damage to the protein subunits by ultraviolet-B (UV-B, 280-320 nm) radiation have been studied in isolated reaction centers of the non-sulfur purple bacterium Rhodobacter sphaeroides R26. UV-B irradiation results in the inhibition of charge separation as detected by the loss of the initial amplitude of absorbance change at 430 nm reflecting the formation of the P+(Q(A)Q(B))- state. In addition to this effect, the charge recombination accelerates and the damping of the semiquinone oscillation increases in the UV-B irradiated reaction centers. A further effect of UV-B is a 2 fold increase in the half- inhibitory concentration of o-phenanthroline. Some damage to the protein subunits of the RC is also observed as a consequence of UV-B irradiation. This effect is manifested as loss of the L, M and H subunits on Coomassie stained gels, but not accompanied with specific degradation products. The damaging effects of UV-B radiation enhanced in reaction centers where the quinone was semireduced (Q(B)-) during UV-B irradiation, but decreased in reaction centers which lacked quinone at the Q(B) binding site. In comparison with Photosystem II of green plant photosynthesis, the bacterial reaction center shows about 40 times lower sensitivity to UV-B radiation concerning the activity loss and 10 times lower sensitivity concerning the extent of reaction center protein damage. It is concluded that the main effect of UV-B radiation in the purple bacterial reaction center occurs at the Q(A)Q(B) quinone acceptor complex by decreasing the binding affinity of Q(B) and shifting the electron equilibration from Q(A)Q(B)- to Q(A)-Q(B). The inhibitory effect is likely to be caused by modification of the protein environment around the Q(B) binding pocket and mediated by the semiquinone form of Q(B). The UV-resistance of the bacterial reaction center compared to Photosystem II indicates that either the Q(A)Q(B) acceptor complex, which is present in both types of reaction centers with similar structure and function, is much less susceptible to UV damage in purple bacteria, or, more likely, that Photosystem II contains UV-B targets which are more sensitive than its quinone complex.

Original languageEnglish
Pages (from-to)171-179
Number of pages9
JournalPhotosynthesis Research
Volume50
Issue number2
Publication statusPublished - 1996

Fingerprint

Rhodobacter sphaeroides
Protein Transport
protein structure
Electron Transport
electron transfer
Photosystem II Protein Complex
ultraviolet radiation
Radiation
Proteobacteria
Protein Subunits
Irradiation
Proteins
quinones
Viridiplantae
Photosynthesis
photosystem II
Genetic Recombination
irradiation
protein subunits
Damping

Keywords

  • bacterial reaction center
  • protein structure
  • UV-B radiation

ASJC Scopus subject areas

  • Plant Science

Cite this

@article{4819ccba70264e048daf70c03603c751,
title = "Resistance of reaction centers from Rhodobacter sphaeroides against UV-B radiation. Effects on protein structure and electron transport",
abstract = "Inhibition of electron transport and damage to the protein subunits by ultraviolet-B (UV-B, 280-320 nm) radiation have been studied in isolated reaction centers of the non-sulfur purple bacterium Rhodobacter sphaeroides R26. UV-B irradiation results in the inhibition of charge separation as detected by the loss of the initial amplitude of absorbance change at 430 nm reflecting the formation of the P+(Q(A)Q(B))- state. In addition to this effect, the charge recombination accelerates and the damping of the semiquinone oscillation increases in the UV-B irradiated reaction centers. A further effect of UV-B is a 2 fold increase in the half- inhibitory concentration of o-phenanthroline. Some damage to the protein subunits of the RC is also observed as a consequence of UV-B irradiation. This effect is manifested as loss of the L, M and H subunits on Coomassie stained gels, but not accompanied with specific degradation products. The damaging effects of UV-B radiation enhanced in reaction centers where the quinone was semireduced (Q(B)-) during UV-B irradiation, but decreased in reaction centers which lacked quinone at the Q(B) binding site. In comparison with Photosystem II of green plant photosynthesis, the bacterial reaction center shows about 40 times lower sensitivity to UV-B radiation concerning the activity loss and 10 times lower sensitivity concerning the extent of reaction center protein damage. It is concluded that the main effect of UV-B radiation in the purple bacterial reaction center occurs at the Q(A)Q(B) quinone acceptor complex by decreasing the binding affinity of Q(B) and shifting the electron equilibration from Q(A)Q(B)- to Q(A)-Q(B). The inhibitory effect is likely to be caused by modification of the protein environment around the Q(B) binding pocket and mediated by the semiquinone form of Q(B). The UV-resistance of the bacterial reaction center compared to Photosystem II indicates that either the Q(A)Q(B) acceptor complex, which is present in both types of reaction centers with similar structure and function, is much less susceptible to UV damage in purple bacteria, or, more likely, that Photosystem II contains UV-B targets which are more sensitive than its quinone complex.",
keywords = "bacterial reaction center, protein structure, UV-B radiation",
author = "J{\'u}lia Tandori and Z. M{\'a}t{\'e} and P. Mar{\'o}ti and I. Vass",
year = "1996",
language = "English",
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TY - JOUR

T1 - Resistance of reaction centers from Rhodobacter sphaeroides against UV-B radiation. Effects on protein structure and electron transport

AU - Tandori, Júlia

AU - Máté, Z.

AU - Maróti, P.

AU - Vass, I.

PY - 1996

Y1 - 1996

N2 - Inhibition of electron transport and damage to the protein subunits by ultraviolet-B (UV-B, 280-320 nm) radiation have been studied in isolated reaction centers of the non-sulfur purple bacterium Rhodobacter sphaeroides R26. UV-B irradiation results in the inhibition of charge separation as detected by the loss of the initial amplitude of absorbance change at 430 nm reflecting the formation of the P+(Q(A)Q(B))- state. In addition to this effect, the charge recombination accelerates and the damping of the semiquinone oscillation increases in the UV-B irradiated reaction centers. A further effect of UV-B is a 2 fold increase in the half- inhibitory concentration of o-phenanthroline. Some damage to the protein subunits of the RC is also observed as a consequence of UV-B irradiation. This effect is manifested as loss of the L, M and H subunits on Coomassie stained gels, but not accompanied with specific degradation products. The damaging effects of UV-B radiation enhanced in reaction centers where the quinone was semireduced (Q(B)-) during UV-B irradiation, but decreased in reaction centers which lacked quinone at the Q(B) binding site. In comparison with Photosystem II of green plant photosynthesis, the bacterial reaction center shows about 40 times lower sensitivity to UV-B radiation concerning the activity loss and 10 times lower sensitivity concerning the extent of reaction center protein damage. It is concluded that the main effect of UV-B radiation in the purple bacterial reaction center occurs at the Q(A)Q(B) quinone acceptor complex by decreasing the binding affinity of Q(B) and shifting the electron equilibration from Q(A)Q(B)- to Q(A)-Q(B). The inhibitory effect is likely to be caused by modification of the protein environment around the Q(B) binding pocket and mediated by the semiquinone form of Q(B). The UV-resistance of the bacterial reaction center compared to Photosystem II indicates that either the Q(A)Q(B) acceptor complex, which is present in both types of reaction centers with similar structure and function, is much less susceptible to UV damage in purple bacteria, or, more likely, that Photosystem II contains UV-B targets which are more sensitive than its quinone complex.

AB - Inhibition of electron transport and damage to the protein subunits by ultraviolet-B (UV-B, 280-320 nm) radiation have been studied in isolated reaction centers of the non-sulfur purple bacterium Rhodobacter sphaeroides R26. UV-B irradiation results in the inhibition of charge separation as detected by the loss of the initial amplitude of absorbance change at 430 nm reflecting the formation of the P+(Q(A)Q(B))- state. In addition to this effect, the charge recombination accelerates and the damping of the semiquinone oscillation increases in the UV-B irradiated reaction centers. A further effect of UV-B is a 2 fold increase in the half- inhibitory concentration of o-phenanthroline. Some damage to the protein subunits of the RC is also observed as a consequence of UV-B irradiation. This effect is manifested as loss of the L, M and H subunits on Coomassie stained gels, but not accompanied with specific degradation products. The damaging effects of UV-B radiation enhanced in reaction centers where the quinone was semireduced (Q(B)-) during UV-B irradiation, but decreased in reaction centers which lacked quinone at the Q(B) binding site. In comparison with Photosystem II of green plant photosynthesis, the bacterial reaction center shows about 40 times lower sensitivity to UV-B radiation concerning the activity loss and 10 times lower sensitivity concerning the extent of reaction center protein damage. It is concluded that the main effect of UV-B radiation in the purple bacterial reaction center occurs at the Q(A)Q(B) quinone acceptor complex by decreasing the binding affinity of Q(B) and shifting the electron equilibration from Q(A)Q(B)- to Q(A)-Q(B). The inhibitory effect is likely to be caused by modification of the protein environment around the Q(B) binding pocket and mediated by the semiquinone form of Q(B). The UV-resistance of the bacterial reaction center compared to Photosystem II indicates that either the Q(A)Q(B) acceptor complex, which is present in both types of reaction centers with similar structure and function, is much less susceptible to UV damage in purple bacteria, or, more likely, that Photosystem II contains UV-B targets which are more sensitive than its quinone complex.

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KW - protein structure

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