Molecular basis of the heat denaturation of photosystem II

Lynmarie K. Thompson, Richard Blaylock, Julian M. Sturtevant, Gary W Brudvig

Research output: Contribution to journalArticle

95 Citations (Scopus)

Abstract

The thermal denaturation of the photosystem II (PSII) membrane protein complex is investigated by assigning the endothermic transitions observed by differential scanning calorimetry (DSC) to the denaturation of particular proteins of the PSII complex. In a prior DSC study of PSII membranes [Thompson, L. K., Sturtevant, J. M., & Brudvig, G. W. (1986) Biochemistry 25, 6161], five DSC peaks were observed in the 30-70°C temperature range (A1, A2, B, C, and D). The A2 peak was assigned to denaturation of a component essential for water oxidation and the B peak to denaturation of a component critical to the remainder of the electron-transport chain. We have now extended these studies with thermal gel analysis and electron paramagnetic resonance (EPR) measurements. Thermal gel analysis, a technique which relies on a change in the solubility properties of a membrane protein upon denaturation, has been used to determine the temperatures of denaturation of all of the major membrane proteins of the PSII complex. EPR experiments have been used to monitor chlorophyll photooxidation and the stability of TyrD+. Peaks B, C, and D in the DSC denaturation profile are each assigned to the denaturaation of several proteins, which provides information on the organization of the PSII complex into structural and functional units. Peak B corresponds to the denaturation of peripheral core proteins and closely associated antenna proteins, peak C to the PSII core, and peak D to the loosely associated antenna proteins. No membrane protein is observed to denature during the A2 peak. The A2 peak is altered by the presence of catalase, superoxide dismutase, low chloride, and high pH. These results suggest that the abnormally sharp A2 peak occurs when the highly oxidizing, sequestered Mn complex (the active site in water oxidation) becomes accessible to the aqueous phase, at elevated temperatures. We propose a mechanism for the reaction of the Mn complex with hydroxide ions, which involves peroxide or superoxide and results in the reduction and release of Mn. The proposed model provides insight into the well-known instability of the Mn complex and the role of chloride in stabilizing the complex. This may enable the future development of purification procedures and may explain the sensitivity of the water-oxidizing apparatus of PSII to heat denaturation.

Original languageEnglish
Pages (from-to)6686-6695
Number of pages10
JournalBiochemistry
Volume28
Issue number16
Publication statusPublished - 1989

Fingerprint

Denaturation
Photosystem II Protein Complex
Hot Temperature
varespladib methyl
Differential Scanning Calorimetry
Membrane Proteins
Differential scanning calorimetry
Electron Spin Resonance Spectroscopy
Temperature
Water
Chlorides
Gels
Paramagnetic resonance
Protein Denaturation
Proteins
Peroxides
Antennas
Chlorophyll
Electron Transport
Protein C

ASJC Scopus subject areas

  • Biochemistry

Cite this

Thompson, L. K., Blaylock, R., Sturtevant, J. M., & Brudvig, G. W. (1989). Molecular basis of the heat denaturation of photosystem II. Biochemistry, 28(16), 6686-6695.

Molecular basis of the heat denaturation of photosystem II. / Thompson, Lynmarie K.; Blaylock, Richard; Sturtevant, Julian M.; Brudvig, Gary W.

In: Biochemistry, Vol. 28, No. 16, 1989, p. 6686-6695.

Research output: Contribution to journalArticle

Thompson, LK, Blaylock, R, Sturtevant, JM & Brudvig, GW 1989, 'Molecular basis of the heat denaturation of photosystem II', Biochemistry, vol. 28, no. 16, pp. 6686-6695.
Thompson LK, Blaylock R, Sturtevant JM, Brudvig GW. Molecular basis of the heat denaturation of photosystem II. Biochemistry. 1989;28(16):6686-6695.
Thompson, Lynmarie K. ; Blaylock, Richard ; Sturtevant, Julian M. ; Brudvig, Gary W. / Molecular basis of the heat denaturation of photosystem II. In: Biochemistry. 1989 ; Vol. 28, No. 16. pp. 6686-6695.
@article{3575c22aa5964ed2873ce191113ac7d3,
title = "Molecular basis of the heat denaturation of photosystem II",
abstract = "The thermal denaturation of the photosystem II (PSII) membrane protein complex is investigated by assigning the endothermic transitions observed by differential scanning calorimetry (DSC) to the denaturation of particular proteins of the PSII complex. In a prior DSC study of PSII membranes [Thompson, L. K., Sturtevant, J. M., & Brudvig, G. W. (1986) Biochemistry 25, 6161], five DSC peaks were observed in the 30-70°C temperature range (A1, A2, B, C, and D). The A2 peak was assigned to denaturation of a component essential for water oxidation and the B peak to denaturation of a component critical to the remainder of the electron-transport chain. We have now extended these studies with thermal gel analysis and electron paramagnetic resonance (EPR) measurements. Thermal gel analysis, a technique which relies on a change in the solubility properties of a membrane protein upon denaturation, has been used to determine the temperatures of denaturation of all of the major membrane proteins of the PSII complex. EPR experiments have been used to monitor chlorophyll photooxidation and the stability of TyrD+. Peaks B, C, and D in the DSC denaturation profile are each assigned to the denaturaation of several proteins, which provides information on the organization of the PSII complex into structural and functional units. Peak B corresponds to the denaturation of peripheral core proteins and closely associated antenna proteins, peak C to the PSII core, and peak D to the loosely associated antenna proteins. No membrane protein is observed to denature during the A2 peak. The A2 peak is altered by the presence of catalase, superoxide dismutase, low chloride, and high pH. These results suggest that the abnormally sharp A2 peak occurs when the highly oxidizing, sequestered Mn complex (the active site in water oxidation) becomes accessible to the aqueous phase, at elevated temperatures. We propose a mechanism for the reaction of the Mn complex with hydroxide ions, which involves peroxide or superoxide and results in the reduction and release of Mn. The proposed model provides insight into the well-known instability of the Mn complex and the role of chloride in stabilizing the complex. This may enable the future development of purification procedures and may explain the sensitivity of the water-oxidizing apparatus of PSII to heat denaturation.",
author = "Thompson, {Lynmarie K.} and Richard Blaylock and Sturtevant, {Julian M.} and Brudvig, {Gary W}",
year = "1989",
language = "English",
volume = "28",
pages = "6686--6695",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "16",

}

TY - JOUR

T1 - Molecular basis of the heat denaturation of photosystem II

AU - Thompson, Lynmarie K.

AU - Blaylock, Richard

AU - Sturtevant, Julian M.

AU - Brudvig, Gary W

PY - 1989

Y1 - 1989

N2 - The thermal denaturation of the photosystem II (PSII) membrane protein complex is investigated by assigning the endothermic transitions observed by differential scanning calorimetry (DSC) to the denaturation of particular proteins of the PSII complex. In a prior DSC study of PSII membranes [Thompson, L. K., Sturtevant, J. M., & Brudvig, G. W. (1986) Biochemistry 25, 6161], five DSC peaks were observed in the 30-70°C temperature range (A1, A2, B, C, and D). The A2 peak was assigned to denaturation of a component essential for water oxidation and the B peak to denaturation of a component critical to the remainder of the electron-transport chain. We have now extended these studies with thermal gel analysis and electron paramagnetic resonance (EPR) measurements. Thermal gel analysis, a technique which relies on a change in the solubility properties of a membrane protein upon denaturation, has been used to determine the temperatures of denaturation of all of the major membrane proteins of the PSII complex. EPR experiments have been used to monitor chlorophyll photooxidation and the stability of TyrD+. Peaks B, C, and D in the DSC denaturation profile are each assigned to the denaturaation of several proteins, which provides information on the organization of the PSII complex into structural and functional units. Peak B corresponds to the denaturation of peripheral core proteins and closely associated antenna proteins, peak C to the PSII core, and peak D to the loosely associated antenna proteins. No membrane protein is observed to denature during the A2 peak. The A2 peak is altered by the presence of catalase, superoxide dismutase, low chloride, and high pH. These results suggest that the abnormally sharp A2 peak occurs when the highly oxidizing, sequestered Mn complex (the active site in water oxidation) becomes accessible to the aqueous phase, at elevated temperatures. We propose a mechanism for the reaction of the Mn complex with hydroxide ions, which involves peroxide or superoxide and results in the reduction and release of Mn. The proposed model provides insight into the well-known instability of the Mn complex and the role of chloride in stabilizing the complex. This may enable the future development of purification procedures and may explain the sensitivity of the water-oxidizing apparatus of PSII to heat denaturation.

AB - The thermal denaturation of the photosystem II (PSII) membrane protein complex is investigated by assigning the endothermic transitions observed by differential scanning calorimetry (DSC) to the denaturation of particular proteins of the PSII complex. In a prior DSC study of PSII membranes [Thompson, L. K., Sturtevant, J. M., & Brudvig, G. W. (1986) Biochemistry 25, 6161], five DSC peaks were observed in the 30-70°C temperature range (A1, A2, B, C, and D). The A2 peak was assigned to denaturation of a component essential for water oxidation and the B peak to denaturation of a component critical to the remainder of the electron-transport chain. We have now extended these studies with thermal gel analysis and electron paramagnetic resonance (EPR) measurements. Thermal gel analysis, a technique which relies on a change in the solubility properties of a membrane protein upon denaturation, has been used to determine the temperatures of denaturation of all of the major membrane proteins of the PSII complex. EPR experiments have been used to monitor chlorophyll photooxidation and the stability of TyrD+. Peaks B, C, and D in the DSC denaturation profile are each assigned to the denaturaation of several proteins, which provides information on the organization of the PSII complex into structural and functional units. Peak B corresponds to the denaturation of peripheral core proteins and closely associated antenna proteins, peak C to the PSII core, and peak D to the loosely associated antenna proteins. No membrane protein is observed to denature during the A2 peak. The A2 peak is altered by the presence of catalase, superoxide dismutase, low chloride, and high pH. These results suggest that the abnormally sharp A2 peak occurs when the highly oxidizing, sequestered Mn complex (the active site in water oxidation) becomes accessible to the aqueous phase, at elevated temperatures. We propose a mechanism for the reaction of the Mn complex with hydroxide ions, which involves peroxide or superoxide and results in the reduction and release of Mn. The proposed model provides insight into the well-known instability of the Mn complex and the role of chloride in stabilizing the complex. This may enable the future development of purification procedures and may explain the sensitivity of the water-oxidizing apparatus of PSII to heat denaturation.

UR - http://www.scopus.com/inward/record.url?scp=0024964924&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0024964924&partnerID=8YFLogxK

M3 - Article

C2 - 2675973

AN - SCOPUS:0024964924

VL - 28

SP - 6686

EP - 6695

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 16

ER -