Evidence against bicarbonate bound in the O2-evolving complex of photosystem II

Gözde Ulas, Gerard Olack, Gary W Brudvig

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

The oxidation of water to molecular oxygen by photosystem II (PSII) is inhibited in bicarbonate-depleted media. One contribution to the inhibition is the binding of bicarbonate to the non-heme iron, which is required for efficient electron transfer on the electron-acceptor side of PSII. There are also proposals that bicarbonate is required for formation of O2 by the manganese-containing O2-evolving complex (OEC). Previous work indicates that a bicarbonate ion does not bind reversibly close to the OEC, but it remains possible that bicarbonate is bound sufficiently tightly to the OEC that it cannot readily exchange with bicarbonate in solution. In this study, we have used NH2OH to destroy the OEC, which would release any tightly bound bicarbonate ions from the active site, and mass spectrometry to detect any released bicarbonate as CO2. The amount of CO2 per PSII released by the NH2OH treatment is observed to be comparable to the background level, although N2O, a product of the reaction of NH 2OH with the OEC, is detected in good yield. These results strongly argue against tightly bound bicarbonate ions in the OEC.

Original languageEnglish
Pages (from-to)3073-3075
Number of pages3
JournalBiochemistry
Volume47
Issue number10
DOIs
Publication statusPublished - Mar 11 2008

Fingerprint

Photosystem II Protein Complex
Bicarbonates
Electrons
Molecular oxygen
Manganese
Mass spectrometry
Mass Spectrometry
Catalytic Domain
Ion exchange
Iron
Oxygen
Oxidation
Water

ASJC Scopus subject areas

  • Biochemistry

Cite this

Evidence against bicarbonate bound in the O2-evolving complex of photosystem II. / Ulas, Gözde; Olack, Gerard; Brudvig, Gary W.

In: Biochemistry, Vol. 47, No. 10, 11.03.2008, p. 3073-3075.

Research output: Contribution to journalArticle

Ulas, Gözde ; Olack, Gerard ; Brudvig, Gary W. / Evidence against bicarbonate bound in the O2-evolving complex of photosystem II. In: Biochemistry. 2008 ; Vol. 47, No. 10. pp. 3073-3075.
@article{2fcefcffa76d41069706b0c07dd4649d,
title = "Evidence against bicarbonate bound in the O2-evolving complex of photosystem II",
abstract = "The oxidation of water to molecular oxygen by photosystem II (PSII) is inhibited in bicarbonate-depleted media. One contribution to the inhibition is the binding of bicarbonate to the non-heme iron, which is required for efficient electron transfer on the electron-acceptor side of PSII. There are also proposals that bicarbonate is required for formation of O2 by the manganese-containing O2-evolving complex (OEC). Previous work indicates that a bicarbonate ion does not bind reversibly close to the OEC, but it remains possible that bicarbonate is bound sufficiently tightly to the OEC that it cannot readily exchange with bicarbonate in solution. In this study, we have used NH2OH to destroy the OEC, which would release any tightly bound bicarbonate ions from the active site, and mass spectrometry to detect any released bicarbonate as CO2. The amount of CO2 per PSII released by the NH2OH treatment is observed to be comparable to the background level, although N2O, a product of the reaction of NH 2OH with the OEC, is detected in good yield. These results strongly argue against tightly bound bicarbonate ions in the OEC.",
author = "G{\"o}zde Ulas and Gerard Olack and Brudvig, {Gary W}",
year = "2008",
month = "3",
day = "11",
doi = "10.1021/bi8000424",
language = "English",
volume = "47",
pages = "3073--3075",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "10",

}

TY - JOUR

T1 - Evidence against bicarbonate bound in the O2-evolving complex of photosystem II

AU - Ulas, Gözde

AU - Olack, Gerard

AU - Brudvig, Gary W

PY - 2008/3/11

Y1 - 2008/3/11

N2 - The oxidation of water to molecular oxygen by photosystem II (PSII) is inhibited in bicarbonate-depleted media. One contribution to the inhibition is the binding of bicarbonate to the non-heme iron, which is required for efficient electron transfer on the electron-acceptor side of PSII. There are also proposals that bicarbonate is required for formation of O2 by the manganese-containing O2-evolving complex (OEC). Previous work indicates that a bicarbonate ion does not bind reversibly close to the OEC, but it remains possible that bicarbonate is bound sufficiently tightly to the OEC that it cannot readily exchange with bicarbonate in solution. In this study, we have used NH2OH to destroy the OEC, which would release any tightly bound bicarbonate ions from the active site, and mass spectrometry to detect any released bicarbonate as CO2. The amount of CO2 per PSII released by the NH2OH treatment is observed to be comparable to the background level, although N2O, a product of the reaction of NH 2OH with the OEC, is detected in good yield. These results strongly argue against tightly bound bicarbonate ions in the OEC.

AB - The oxidation of water to molecular oxygen by photosystem II (PSII) is inhibited in bicarbonate-depleted media. One contribution to the inhibition is the binding of bicarbonate to the non-heme iron, which is required for efficient electron transfer on the electron-acceptor side of PSII. There are also proposals that bicarbonate is required for formation of O2 by the manganese-containing O2-evolving complex (OEC). Previous work indicates that a bicarbonate ion does not bind reversibly close to the OEC, but it remains possible that bicarbonate is bound sufficiently tightly to the OEC that it cannot readily exchange with bicarbonate in solution. In this study, we have used NH2OH to destroy the OEC, which would release any tightly bound bicarbonate ions from the active site, and mass spectrometry to detect any released bicarbonate as CO2. The amount of CO2 per PSII released by the NH2OH treatment is observed to be comparable to the background level, although N2O, a product of the reaction of NH 2OH with the OEC, is detected in good yield. These results strongly argue against tightly bound bicarbonate ions in the OEC.

UR - http://www.scopus.com/inward/record.url?scp=40549106743&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=40549106743&partnerID=8YFLogxK

U2 - 10.1021/bi8000424

DO - 10.1021/bi8000424

M3 - Article

VL - 47

SP - 3073

EP - 3075

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 10

ER -