Amphipols and Photosynthetic Light-Harvesting Pigment-Protein Complexes
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The trimeric light-harvesting complexes II (LHCII) of plants and green algae are pigment-protein complexes involved in light harvesting and photoprotection. Different conformational states have been proposed to be responsible for their different functions. At present, detergent-solubilized LHCII is used as a model for the “light-harvesting conformation”, whereas the “quenched conformation” is mimicked by LHCII aggregates. However, none of these conditions seem to perfectly reproduce the properties of LHCII in vivo. In addition, several monomeric LHC complexes are not fully stable in detergent. There is thus a need to find conditions that allow analyzing LHCs in vitro in stable and, hopefully, more native-like conformations. Here, we report a study of LHCII, the major antenna complex of plants, in complex with amphipols. We have trapped trimeric LHCII and monomeric Lhcb1 with either polyanionic or non-ionic amphipols and studied the effect of these polymers on the properties of the complexes. We show that, as compared to detergent solutions, amphipols have a stabilizing effect on LHCII. We also show that the average fluorescence lifetime of LHCII trapped in an anionic amphipol is ~30 % shorter than in α-dodecylmaltoside, due to the presence of a conformation with 230-ps lifetime that is not present in detergent solutions.
KeywordsNeoxanthin Fluorescence Light-harvesting complexes Membrane protein A8-35 Non-ionic amphipols
A specific type of polyacrylate-based amphipol
A specific batch of non-ionic APol
Size exclusion chromatography
Thiol-based transfer agent
Particular thanks are due to Roberta Croce (VU University Amsterdam) for her support and help throughout this work, as well as for contributing to its writing. We also thank Laura M. Roy and Bart Sasbrink (VU University Amsterdam) for critical reading of the manuscript, and Pengqi Xu for his help with generating Fig. 7. This project was supported by the Chemical Science division of the Netherlands organization for scientific research (NWO-CW) via an ECHO grant to R. Croce, by the CNRS, by University Paris-7, and by the “Initiative d’Excellence” program from the French State (Grant “DYNAMO”, ANR-11-LABX-0011-01).
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