Kinetic nature of the thermal destabilization of LHCII macroaggregates

• Published in: Journal of photochemistry and photobiology. B, Biology Biology, 2005-02, Vol.78 (2), p.165-170
• Main Authors: Krumova, Sashka B., Todinova, Svetla J., Busheva, Mira C., Taneva, Stefka G.
• Format: Article
• Language: English
• Subjects: Calorimetric enthalpy; Calorimetry, Differential Scanning; Denaturation transition; Differential scanning calorimetry; Enzyme Stability; Fluorescence emission; Kinetics; Light-harvesting chlorophyll a/b pigment–protein complex; Photosystem II Protein Complex - chemistry; Photosystem II Protein Complex - isolation & purification; Photosystem II Protein Complex - metabolism; Pisum sativum - enzymology; Protein Denaturation; Spectrometry, Fluorescence; Spinacia oleracea - enzymology; Temperature
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2004.11.005

The main light-harvesting chl a/b pigment–protein complex of photosystem II (LHCII) in isolated state forms macroaggregates with different ultrastructure and lipid content [I. Simidjiev, V. Barzda, L. Mustardy, G. Garab, Anal. Biochem. 250 (1997) 169–175]. The thermodynamic stability of highly delipidated tightly bound LHCII macroaggregates is studied by differential scanning calorimetry and fluorescence spectroscopy. The calorimetric profile of LHCII is asymmetric, the denaturation transition is taking place at around 72 °C. A shoulder, which overlaps with the main denaturation transition, appears around 58 °C. The denaturation temperature strongly depends on the scanning rate indicating the kinetic nature of the thermal destabilization of LHCII macroaggregates. The fluorescence data prove that the thermal denaturation of LHCII is an irreversible and kinetically controlled process.