Investigation of the inhibitory effect of nitrite on photosystem II

Ravi Pokhrel, Gary W Brudvig

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The role of chloride in photosystem II (PSII) is unclear. Several monovalent anions compete for the Cl- site(s) in PSII, and some even support activity. NO2 - has been reported to be an activator in Cl--depleted PSII membranes. In this paper, we report a detailed investigation of the chemistry of NO2 - with PSII. NO2 - is shown to inhibit PSII activity, and the effects on the donor side as well as the acceptor side are characterized using steady-state O2-evolution assays, electron paramagnetic resonance (EPR) spectroscopy, electron-transfer assays, and flash-induced polarographic O2 yield measurements. Enzyme kinetics analysis shows multiple sites of NO2 - inhibition in PSII with significant inhibition of oxygen evolution at 2 -. By EPR spectroscopy, the yield of the S2 state remains unchanged up to 15 mM NO 2 -. However, the S2-state g = 4.1 signal is favored over the g = 2 multiline signal with increasing NO2 - concentrations. This could indicate competition of NO 2 - for the Cl- site at higher NO 2 - concentrations. In addition to the donor-side chemistry, there is clear evidence of an acceptor-side effect of NO 2 -. The g = 1.9 Fe(II)-QA -• signal is replaced by a broad g = 1.6 signal in the presence of NO 2 -. Additionally, a g = 1.8 Fe(II)-Q-• signal is present in the dark, indicating the formation of a NO2 --bound Fe(II)-QB -• species in the dark. Electron-transfer assays suggest that the inhibitory effect of NO 2 - on the activity of PSII is largely due to the donor-side chemistry of NO2 -. UV-visible spectroscopy and flash-induced polarographic O2 yield measurements indicate that NO2 - is oxidized by the oxygen-evolving complex in the higher S states, contributing to the donor-side inhibition by NO 2 -.

Original languageEnglish
Pages (from-to)3781-3789
Number of pages9
JournalBiochemistry
Volume52
Issue number21
DOIs
Publication statusPublished - May 28 2013

Fingerprint

Photosystem II Protein Complex
Nitrites
Assays
Spectrum Analysis
Electron Spin Resonance Spectroscopy
Paramagnetic resonance
Spectroscopy
Electrons
Oxygen
Enzyme kinetics
Electron spectroscopy
Anions
Chlorides
Membranes
Enzymes

ASJC Scopus subject areas

  • Biochemistry

Cite this

Investigation of the inhibitory effect of nitrite on photosystem II. / Pokhrel, Ravi; Brudvig, Gary W.

In: Biochemistry, Vol. 52, No. 21, 28.05.2013, p. 3781-3789.

Research output: Contribution to journalArticle

@article{6bcf92bce32b4b8899506907cc507a8f,
title = "Investigation of the inhibitory effect of nitrite on photosystem II",
abstract = "The role of chloride in photosystem II (PSII) is unclear. Several monovalent anions compete for the Cl- site(s) in PSII, and some even support activity. NO2 - has been reported to be an activator in Cl--depleted PSII membranes. In this paper, we report a detailed investigation of the chemistry of NO2 - with PSII. NO2 - is shown to inhibit PSII activity, and the effects on the donor side as well as the acceptor side are characterized using steady-state O2-evolution assays, electron paramagnetic resonance (EPR) spectroscopy, electron-transfer assays, and flash-induced polarographic O2 yield measurements. Enzyme kinetics analysis shows multiple sites of NO2 - inhibition in PSII with significant inhibition of oxygen evolution at 2 -. By EPR spectroscopy, the yield of the S2 state remains unchanged up to 15 mM NO 2 -. However, the S2-state g = 4.1 signal is favored over the g = 2 multiline signal with increasing NO2 - concentrations. This could indicate competition of NO 2 - for the Cl- site at higher NO 2 - concentrations. In addition to the donor-side chemistry, there is clear evidence of an acceptor-side effect of NO 2 -. The g = 1.9 Fe(II)-QA -• signal is replaced by a broad g = 1.6 signal in the presence of NO 2 -. Additionally, a g = 1.8 Fe(II)-Q-• signal is present in the dark, indicating the formation of a NO2 --bound Fe(II)-QB -• species in the dark. Electron-transfer assays suggest that the inhibitory effect of NO 2 - on the activity of PSII is largely due to the donor-side chemistry of NO2 -. UV-visible spectroscopy and flash-induced polarographic O2 yield measurements indicate that NO2 - is oxidized by the oxygen-evolving complex in the higher S states, contributing to the donor-side inhibition by NO 2 -.",
author = "Ravi Pokhrel and Brudvig, {Gary W}",
year = "2013",
month = "5",
day = "28",
doi = "10.1021/bi400206q",
language = "English",
volume = "52",
pages = "3781--3789",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "21",

}

TY - JOUR

T1 - Investigation of the inhibitory effect of nitrite on photosystem II

AU - Pokhrel, Ravi

AU - Brudvig, Gary W

PY - 2013/5/28

Y1 - 2013/5/28

N2 - The role of chloride in photosystem II (PSII) is unclear. Several monovalent anions compete for the Cl- site(s) in PSII, and some even support activity. NO2 - has been reported to be an activator in Cl--depleted PSII membranes. In this paper, we report a detailed investigation of the chemistry of NO2 - with PSII. NO2 - is shown to inhibit PSII activity, and the effects on the donor side as well as the acceptor side are characterized using steady-state O2-evolution assays, electron paramagnetic resonance (EPR) spectroscopy, electron-transfer assays, and flash-induced polarographic O2 yield measurements. Enzyme kinetics analysis shows multiple sites of NO2 - inhibition in PSII with significant inhibition of oxygen evolution at 2 -. By EPR spectroscopy, the yield of the S2 state remains unchanged up to 15 mM NO 2 -. However, the S2-state g = 4.1 signal is favored over the g = 2 multiline signal with increasing NO2 - concentrations. This could indicate competition of NO 2 - for the Cl- site at higher NO 2 - concentrations. In addition to the donor-side chemistry, there is clear evidence of an acceptor-side effect of NO 2 -. The g = 1.9 Fe(II)-QA -• signal is replaced by a broad g = 1.6 signal in the presence of NO 2 -. Additionally, a g = 1.8 Fe(II)-Q-• signal is present in the dark, indicating the formation of a NO2 --bound Fe(II)-QB -• species in the dark. Electron-transfer assays suggest that the inhibitory effect of NO 2 - on the activity of PSII is largely due to the donor-side chemistry of NO2 -. UV-visible spectroscopy and flash-induced polarographic O2 yield measurements indicate that NO2 - is oxidized by the oxygen-evolving complex in the higher S states, contributing to the donor-side inhibition by NO 2 -.

AB - The role of chloride in photosystem II (PSII) is unclear. Several monovalent anions compete for the Cl- site(s) in PSII, and some even support activity. NO2 - has been reported to be an activator in Cl--depleted PSII membranes. In this paper, we report a detailed investigation of the chemistry of NO2 - with PSII. NO2 - is shown to inhibit PSII activity, and the effects on the donor side as well as the acceptor side are characterized using steady-state O2-evolution assays, electron paramagnetic resonance (EPR) spectroscopy, electron-transfer assays, and flash-induced polarographic O2 yield measurements. Enzyme kinetics analysis shows multiple sites of NO2 - inhibition in PSII with significant inhibition of oxygen evolution at 2 -. By EPR spectroscopy, the yield of the S2 state remains unchanged up to 15 mM NO 2 -. However, the S2-state g = 4.1 signal is favored over the g = 2 multiline signal with increasing NO2 - concentrations. This could indicate competition of NO 2 - for the Cl- site at higher NO 2 - concentrations. In addition to the donor-side chemistry, there is clear evidence of an acceptor-side effect of NO 2 -. The g = 1.9 Fe(II)-QA -• signal is replaced by a broad g = 1.6 signal in the presence of NO 2 -. Additionally, a g = 1.8 Fe(II)-Q-• signal is present in the dark, indicating the formation of a NO2 --bound Fe(II)-QB -• species in the dark. Electron-transfer assays suggest that the inhibitory effect of NO 2 - on the activity of PSII is largely due to the donor-side chemistry of NO2 -. UV-visible spectroscopy and flash-induced polarographic O2 yield measurements indicate that NO2 - is oxidized by the oxygen-evolving complex in the higher S states, contributing to the donor-side inhibition by NO 2 -.

UR - http://www.scopus.com/inward/record.url?scp=84878320480&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84878320480&partnerID=8YFLogxK

U2 - 10.1021/bi400206q

DO - 10.1021/bi400206q

M3 - Article

VL - 52

SP - 3781

EP - 3789

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 21

ER -