Heat-induced disassembly and degradation of chlorophyll-containing protein complexes in vivo

• Published in: Biochimica et biophysica acta Vol. 1797; no. 1; pp. 63 - 70
• Main Authors: Lípová, Lenka, Krchňák, Pavel, Komenda, Josef, Ilík, Petr
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 2010
• Subjects: Chlorophyll - analysis; Chlorophyll fluorescence temperature curve, Disassembly; Chlorophyll-containing protein complex; Heat denaturation; High temperature; Hordeum - metabolism; Hot Temperature; Light; Light-Harvesting Protein Complexes - chemistry; Light-Harvesting Protein Complexes - metabolism; Molecular Weight; Native electrophoresis; Photosynthesis; Pigments, Biological - analysis; Plant Leaves - chemistry; Plant Leaves - metabolism; Plant Leaves - radiation effects; Thermodynamics; Thylakoids - chemistry; Chlorophyll-containing protein complex; Heat denaturation; High temperature; Native electrophoresis; Chlorophyll fluorescence temperature curve, Disassembly
• ISSN: 0005-2728; 0006-3002; 1879-2650
• DOI: 10.1016/j.bbabio.2009.08.001

Gradual heating of green leaves up to non-physiological temperatures is often used to estimate thermal stability of photosynthetic apparatus. However, a complete sequence of heat-induced disassembly and denaturation of chlorophyll-containing protein complexes (CPCs) has not been reported yet. In this work, we heated (1 °C·min − 1 ) barley leaves to temperatures selected according to the changes in the chlorophyll fluorescence temperature curve (FTC) and we analyzed CPC stability by two-dimensional native Deriphat/SDS–PAGE . The first distinct change in both structure and function of photosystem II (PSII) appeared at 40–50 °C. PSII core (CCII) dimers began to dissociate monomers, which was accompanied by a decrease in PSII photochemistry and reflected in FTC as the first fluorescence increase. Further changes in CPCs appeared at 57–60 °C, when FTC increases to its second maximum. Photosystem I (PSI) cores (CCI) partially dissociated from light-harvesting complexes of PSI (LHCI) and formed aggregates. The rest of CCI–LHCI complexes, as well as the CCI aggregates, degraded to the PSI-A/B heterodimer in leaves heated to 70 °C. Heating to these temperatures led to a complete degradation of CCII components and corresponding loss of PSII photochemistry. Trimeric light-harvesting complexes of PSII (LHCII) markedly dissociated to monomers and denatured, as evidenced by a release of large amount of free chlorophylls. Between 70 and 80 °C, a complete degradation of LHCII occurred, leaving the PSI-A/B heterodimer as the only detectable CPC in the membrane. This most thermostable CPC disappeared after heating to 90 °C, which corresponded to a loss of PSI photochemistry.