Necessary Components of NPQ (qE)

1. pH gradient

2. Conversion of Violaxanthin to Zeaxanthin1

? Epoxidase Enzyme: ideal pH = 8.0

? Depoxidase Enzyme: ideal pH = 5.2

3. PsbS (a.k.a. CP22)2

2X.P. Li, et al., Nature, 2000, 403, 391.

1P. Müller, et al., Plant Physiology, 2001, 125, 1558.

Zeaxanthin

Antheraxanthin

Violaxanthin

excess

limiting