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  • Title: Dynamics of zeaxanthin binding to the photosystem II monomeric antenna protein Lhcb6 (CP24) and modulation of its photoprotection properties.
    Author: Betterle N, Ballottari M, Hienerwadel R, Dall'Osto L, Bassi R.
    Journal: Arch Biochem Biophys; 2010 Dec 01; 504(1):67-77. PubMed ID: 20494647.
    Abstract:
    Lhcb6 (CP24) is a monomeric antenna protein of photosystem II, which has been shown to play special roles in photoprotective mechanisms, such as the Non-Photochemical Quenching and reorganization of grana membranes in excess light conditions. In this work we analyzed Lhcb6 in vivo and in vitro: we show this protein, upon activation of the xanthophyll cycle, accumulates zeaxanthin into inner binding sites faster and to a larger extent than any other pigment-protein complex. By comparative analysis of Lhcb6 complexes violaxanthin or zeaxanthin binding, we demonstrate that zeaxanthin not only down-regulates chlorophyll singlet excited states, but also increases the efficiency of chlorophyll triplet quenching, with consequent reduction of singlet oxygen production and significant enhancement of photo-stability. On these bases we propose that Lhcb6, the most recent addition to the Lhcb protein family which evolved concomitantly to the adaptation of photosynthesis to land environment, has a crucial role in zeaxanthin-dependent photoprotection.
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