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Membrane curvature stress controls the maximal conversion of violaxanthin to zeaxanthin in the violaxanthin cycle - influence of alpha-tocopherol, cetylethers, linolenic acid, and temperature

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Author

Summary, in English

Zeaxanthin, an important component in protection against overexcitation in higher plants, is formed from violaxanthin by the enzyme violaxanthin de-epoxidase. We have investigated factors that may control the maximal degree of conversion in the violaxanthin cycle. The conversion of violaxanthin to zeaxanthin in isolated spinach thylakoids was followed at different temperatures and in the presence of lipid packing modifiers. The maximum degree of conversion was found to be 35%, 70% and 80% at 4 'C, 25 'C and 37 'C respectively. In the presence of membrane modifying agents, known to promote non-lamellar structures (Hit), such as linolenic acid the conversion increased, and the maximal level of violaxanthin deepoxidation obtained was close to 100%. In contrast, substances promoting lamellar phases (L.), such as alpha-tocopherol and 8-cetylether (C16EO8), only 55% and 35% of the violaxanthin was converted at 25 degrees C, respectively. The results are interpreted in light of the lipid composition of the thylakoid membrane, and we propose a model where a negative curvature elastic stress in the thylakoid lipid bilayer is required for violaxanthin deepoxidase activity. In this model zeaxanthin with its longer hydrophobic stretch is proposed to promote lamellar arrangements of the membrane. As a result, zeaxanthin relieves the curvature elastic stress, which in turn leads to inactivation of violaxanthin de-epoxidase. (c) 2007 Elsevier B.V. All rights reserved.

Publishing year

2007

Language

English

Pages

2310-2318

Publication/Series

Biochimica et Biophysica Acta - Biomembranes

Volume

1768

Issue

9

Document type

Journal article

Publisher

Elsevier

Topic

  • Biological Sciences

Keywords

  • zeaxanthin
  • violaxanthin de-epoxidase (VDE)
  • membrane
  • thylakoid
  • membrane curvature stress
  • inverted hexagonal phase (H-II)
  • xanthophyll cycle

Status

Published

ISBN/ISSN/Other

  • ISSN: 0005-2736