Very rapid phosphorylation kinetics suggest a unique role for Lhcb2 during state transitions in Arabidopsis
Plant J. 2013;76 (2):236-246
Leoni C, Pietrzykowska M, Kiss AZ, Suorsa M, Ceci LR, Aro EM, Jansson S

Abstract
The light harvesting complex II (LHCII) contains three highly homologous chlorophyll-a/b-binding proteins (Lhcb1, Lhcb2 and Lhcb3), which can be assembled into both homo- and heterotrimers. Lhcb1 and Lhcb2 are reversibly phosphorylated by the action of the STN7 kinase and the PPH1/TAP38 phosphatase in the so-called state transition process. We have developed antibodies specific for the phosphorylated forms of Lhcb1 and Lhcb2. We found that Lhcb2 is more rapidly phosphorylated than Lhcb1: 10 seconds of "state 2 light" results in Lhcb2 phosphorylation to 30% of the maximum level. Phosphorylated and non-phosphorylated forms of the proteins showed no difference in electrophoretic mobility and dephosphorylation kinetics did not differ between the two proteins. In state 2,most of the phosphorylated forms of Lhcb1 and Lhcb2 were present in super- and megacomplexes comprising both PSI and PSII, and the state 2-specific PSI-LHCII complex was highly enriched in the phosphorylated forms of Lhcb2. Our results imply distinct and specific roles for Lhcb1 and Lhcb2 in the regulation of photosynthetic light harvesting. This article is protected by copyright. All rights reserved.
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