TY - JOUR
T1 - Differential Scanning Calorimetry of Chloroplast Membranes
T2 - Identification of an Endothermic Transition Associated with the Water-Splitting Complex of Photosystem II
AU - Cramer, William A.
AU - Whitmarsh, John
AU - Low, Philip S.
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 1981/1
Y1 - 1981/1
N2 - The structure of spinach thylakoid membranes has been investigated by sensitive differential scanning calorimetry. Six endotherms are observed between 20 and 85°C, corresponding to order-disorder transitions of different structural domains within the thylakoid membrane. In a medium of relatively high ionic strength, endothermic transitions occur at 42, 54, 65, 72, 79, and 84°C, with the 65°C transition being particularly prominent. At a lower ionic strength, transitions are centered at 44, 61, 66, 70, 78, and 83°C. The 42-44°C endothermic transition (the A transition) can be correlated with the modification of three electron-transport components or properties associated with photosystem II: (i) release of manganese from the membrane, (ii) the loss of O2 evolution with water as a donor, and (iii) a decrease in the redox potential of the hydroquinone-reducible cytochrome b-559. Both the A transition and the ability to evolve O2 are irreversibly lost after heating to 49°C and also after exposure to trypsin, suggesting the involvement of protein in this transition. The interpretation of these observations is that one effect of the A transition involves the thermal disruption of a protein component on the donor side of photosystem II.
AB - The structure of spinach thylakoid membranes has been investigated by sensitive differential scanning calorimetry. Six endotherms are observed between 20 and 85°C, corresponding to order-disorder transitions of different structural domains within the thylakoid membrane. In a medium of relatively high ionic strength, endothermic transitions occur at 42, 54, 65, 72, 79, and 84°C, with the 65°C transition being particularly prominent. At a lower ionic strength, transitions are centered at 44, 61, 66, 70, 78, and 83°C. The 42-44°C endothermic transition (the A transition) can be correlated with the modification of three electron-transport components or properties associated with photosystem II: (i) release of manganese from the membrane, (ii) the loss of O2 evolution with water as a donor, and (iii) a decrease in the redox potential of the hydroquinone-reducible cytochrome b-559. Both the A transition and the ability to evolve O2 are irreversibly lost after heating to 49°C and also after exposure to trypsin, suggesting the involvement of protein in this transition. The interpretation of these observations is that one effect of the A transition involves the thermal disruption of a protein component on the donor side of photosystem II.
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U2 - 10.1021/bi00504a026
DO - 10.1021/bi00504a026
M3 - Article
C2 - 7470468
AN - SCOPUS:0019873804
VL - 20
SP - 157
EP - 162
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 1
ER -