RESEARCH: VDE-STRUCTURE-PH
FOLDING PROJECT #19335 PROFILE

Plants change how they photosynthesize based on light. A process called the xanthophyll cycle helps them deal with strong light by converting a pigment called violaxanthin into zeaxanthin. This protects plants from damage. Researchers studied an enzyme called VDE, which is key to this cycle. They found that VDE changes shape depending on the acidity of its surroundings, allowing it to work properly and help plants adapt to different light conditions.

Note: This TLDR is a simplication and may not be 100% accurate.

To adapt to shifting lighting conditions, plants modify their photosynthetic activity.

The xanthophyll cycle, in which the carotenoid violaxanthin is transformed into zeaxanthin in strong light, plays a key role in controlling photosynthesis.

This process activates the disposal of excess absorbed energy as heat and the scavenging of reactive oxygen species.

When photosynthetic electron transport exceeds the capacity of assimilatory reactions, violaxanthin deepoxidase (VDE), the enzyme responsible for zeaxanthin synthesis, is activated by the acidification of the thylakoid lumen.

At neutral pH, VDE is a soluble and inactive enzyme, but at acidic pH, it attaches to the thylakoid membrane where it binds its substrate.

Ascorbate is used by VDE as a cosubstrate as well, and its pH-dependent Km may indicate a preference for ascorbic acid.

At neutral and acidic pH, we established the structures of the central lipocalin domain of VDE (VDEcd).

VDEcd is monomeric and has its active site blocked by a lipocalin barrel at neutral pH.

The barrel unwinds and the enzyme emerges as a dimer during acidification.

The two violaxanthin beta-ionone rings may be deep oxidized simultaneously in two channels that connect the two active sites of the dimer, giving VDE an ideal example of an asymmetric enzyme's adaptation to its symmetric substrate.

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Photosynthesis

The process by which plants convert light energy into chemical energy.

Photosynthesis is how plants make food using sunlight. They take in carbon dioxide and water and use the sun's energy to create glucose (sugar), releasing oxygen as a byproduct.

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Xanthophyll Cycle

A series of chemical reactions in plants that regulate light absorption and energy dissipation.

The xanthophyll cycle helps plants adjust to changing light conditions. It involves the conversion of carotenoids like violaxanthin into zeaxanthin, which protects plants from excess light damage.

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Violaxanthin

A type of carotenoid pigment found in plants.

Violaxanthin is a yellow pigment that helps protect plants from too much light. It can be converted to zeaxanthin during bright conditions.

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Zeaxanthin

A type of carotenoid pigment found in plants.

Zeaxanthin is a yellow-orange pigment that helps protect plants from excess light. It's produced when violaxanthin is converted during bright conditions.

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Violaxanthin Deepoxidase (VDE)

Violaxanthin Deepoxidase

VDE is an enzyme that converts violaxanthin into zeaxanthin in plants. This process helps protect plants from excess light.

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Thylakoid Lumen

The internal space enclosed by the thylakoid membrane in chloroplasts.

The thylakoid lumen is a compartment within chloroplasts where photosynthesis takes place. It's important for maintaining the pH balance needed for VDE activity.

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Ascorbate

A water-soluble antioxidant also known as vitamin C.

Ascorbate is an important molecule in plants for protecting against oxidative stress. It can act as a cosubstrate for VDE.