Synthetic quinones influencing herbicide binding and Photosystem II electron transport. The effects of triazine-resistance on quinone binding properties in thylakoid membranes

Willem Vermaas, Charles J. Arntzen

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43 Citations (Scopus)

Abstract

We have analyzed the binding of synthetic quinones and herbicides which inhibit electron transport at the acceptor side of Photosystem II (PS II) of the photosynthetic electron-transport chain in thylakoid membranes. These data show that quinones and PS II-directed herbicides compete for binding to a common binding environment within a PS II region which functions as the Q- PQ oxidoreductase. We observed that (1) synthetic quinones cause a parallel inhibition of electron transport and [14C]herbicide displacement, and (2) herbicide binding is affected both by the fully oxidized and fully reduced form of a quinone. Quinone function and inhibitor binding were also investigated in thylakoids isolated from triazine-resistant weed biotypes. We conclude the following. (1) The affinity of the secondary accepting quinone, B, is decreased in resistant thylakoids. (2) The observation that the equilibrium concentration of reduced Q after transferring one electron to the acceptor side of PS II is increased in resistant as compared to susceptible chloroplasts may be explained both by a decrease in the affinity of PQ for the herbicide / quinone binding environment, and by a decrease of the midpont redox potential of the B B- couple. (3) The binding environment regulating quinone and herbicide affinity may be divided roughly into two domains; we suggest that the domain regulating quinone head-group binding is little changed in resistant membranes, whereas the domain-regulating quinone side-group binding (and atrazine) is altered. This results in increased inhibitory activity of tetrachloro-p-benzoquinone and phenolic herbicides, which are hypothesized to utilize the quinone head-group domain. The two domains appear to be spatially overlapping because efficient atrazine displacement by tetrachloro-p-benzoquinone is observed.

Original languageEnglish (US)
Pages (from-to)483-491
Number of pages9
JournalBBA - Bioenergetics
Volume725
Issue number3
DOIs
StatePublished - Dec 30 1983
Externally publishedYes

Fingerprint

Quinones
Triazines
Thylakoids
Photosystem II Protein Complex
Herbicides
Electron Transport
Membranes
Atrazine
benzoquinone
Chloroplasts
Oxidation-Reduction
Oxidoreductases
Electrons

Keywords

  • Electron transport
  • Herbicide
  • Photosystem II
  • Plastoquinone
  • Quinone
  • Thylakoid membrane

ASJC Scopus subject areas

  • Biophysics

Cite this

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title = "Synthetic quinones influencing herbicide binding and Photosystem II electron transport. The effects of triazine-resistance on quinone binding properties in thylakoid membranes",
abstract = "We have analyzed the binding of synthetic quinones and herbicides which inhibit electron transport at the acceptor side of Photosystem II (PS II) of the photosynthetic electron-transport chain in thylakoid membranes. These data show that quinones and PS II-directed herbicides compete for binding to a common binding environment within a PS II region which functions as the Q- PQ oxidoreductase. We observed that (1) synthetic quinones cause a parallel inhibition of electron transport and [14C]herbicide displacement, and (2) herbicide binding is affected both by the fully oxidized and fully reduced form of a quinone. Quinone function and inhibitor binding were also investigated in thylakoids isolated from triazine-resistant weed biotypes. We conclude the following. (1) The affinity of the secondary accepting quinone, B, is decreased in resistant thylakoids. (2) The observation that the equilibrium concentration of reduced Q after transferring one electron to the acceptor side of PS II is increased in resistant as compared to susceptible chloroplasts may be explained both by a decrease in the affinity of PQ for the herbicide / quinone binding environment, and by a decrease of the midpont redox potential of the B B- couple. (3) The binding environment regulating quinone and herbicide affinity may be divided roughly into two domains; we suggest that the domain regulating quinone head-group binding is little changed in resistant membranes, whereas the domain-regulating quinone side-group binding (and atrazine) is altered. This results in increased inhibitory activity of tetrachloro-p-benzoquinone and phenolic herbicides, which are hypothesized to utilize the quinone head-group domain. The two domains appear to be spatially overlapping because efficient atrazine displacement by tetrachloro-p-benzoquinone is observed.",
keywords = "Electron transport, Herbicide, Photosystem II, Plastoquinone, Quinone, Thylakoid membrane",
author = "Willem Vermaas and Arntzen, {Charles J.}",
year = "1983",
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T1 - Synthetic quinones influencing herbicide binding and Photosystem II electron transport. The effects of triazine-resistance on quinone binding properties in thylakoid membranes

AU - Vermaas, Willem

AU - Arntzen, Charles J.

PY - 1983/12/30

Y1 - 1983/12/30

N2 - We have analyzed the binding of synthetic quinones and herbicides which inhibit electron transport at the acceptor side of Photosystem II (PS II) of the photosynthetic electron-transport chain in thylakoid membranes. These data show that quinones and PS II-directed herbicides compete for binding to a common binding environment within a PS II region which functions as the Q- PQ oxidoreductase. We observed that (1) synthetic quinones cause a parallel inhibition of electron transport and [14C]herbicide displacement, and (2) herbicide binding is affected both by the fully oxidized and fully reduced form of a quinone. Quinone function and inhibitor binding were also investigated in thylakoids isolated from triazine-resistant weed biotypes. We conclude the following. (1) The affinity of the secondary accepting quinone, B, is decreased in resistant thylakoids. (2) The observation that the equilibrium concentration of reduced Q after transferring one electron to the acceptor side of PS II is increased in resistant as compared to susceptible chloroplasts may be explained both by a decrease in the affinity of PQ for the herbicide / quinone binding environment, and by a decrease of the midpont redox potential of the B B- couple. (3) The binding environment regulating quinone and herbicide affinity may be divided roughly into two domains; we suggest that the domain regulating quinone head-group binding is little changed in resistant membranes, whereas the domain-regulating quinone side-group binding (and atrazine) is altered. This results in increased inhibitory activity of tetrachloro-p-benzoquinone and phenolic herbicides, which are hypothesized to utilize the quinone head-group domain. The two domains appear to be spatially overlapping because efficient atrazine displacement by tetrachloro-p-benzoquinone is observed.

AB - We have analyzed the binding of synthetic quinones and herbicides which inhibit electron transport at the acceptor side of Photosystem II (PS II) of the photosynthetic electron-transport chain in thylakoid membranes. These data show that quinones and PS II-directed herbicides compete for binding to a common binding environment within a PS II region which functions as the Q- PQ oxidoreductase. We observed that (1) synthetic quinones cause a parallel inhibition of electron transport and [14C]herbicide displacement, and (2) herbicide binding is affected both by the fully oxidized and fully reduced form of a quinone. Quinone function and inhibitor binding were also investigated in thylakoids isolated from triazine-resistant weed biotypes. We conclude the following. (1) The affinity of the secondary accepting quinone, B, is decreased in resistant thylakoids. (2) The observation that the equilibrium concentration of reduced Q after transferring one electron to the acceptor side of PS II is increased in resistant as compared to susceptible chloroplasts may be explained both by a decrease in the affinity of PQ for the herbicide / quinone binding environment, and by a decrease of the midpont redox potential of the B B- couple. (3) The binding environment regulating quinone and herbicide affinity may be divided roughly into two domains; we suggest that the domain regulating quinone head-group binding is little changed in resistant membranes, whereas the domain-regulating quinone side-group binding (and atrazine) is altered. This results in increased inhibitory activity of tetrachloro-p-benzoquinone and phenolic herbicides, which are hypothesized to utilize the quinone head-group domain. The two domains appear to be spatially overlapping because efficient atrazine displacement by tetrachloro-p-benzoquinone is observed.

KW - Electron transport

KW - Herbicide

KW - Photosystem II

KW - Plastoquinone

KW - Quinone

KW - Thylakoid membrane

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EP - 491

JO - Biochimica et Biophysica Acta - Bioenergetics

JF - Biochimica et Biophysica Acta - Bioenergetics

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