Control of the light harvesting function of chloroplast membranes: the LHCII-aggregation model for non-photochemical quenching.

Dissipation of excess excitation energy within the photosystem II light-harvesting antenna (LHCII) by non-photochemical quenching (NPQ) is an important photoprotective process in plants. An update to a hypothesis for the mechanism of NPQ [FEBS Letters 292, 1991] is presented. The impact of recent advances in understanding the structure, organisation and photophysics of LHCII is assessed. We show possible locations of the predicted regulatory and quenching pigment-binding sites in the structural model of the major LHCII. We suggest that NPQ is a highly regulated concerted response of the organised thylakoid macrostructure, which can include different mechanisms and sites at different times.