Light-harvesting complexes access analogue emissive states in different environments

Vincenzo Mascoli, Andrius Gelzinis, Jevgenij Chmeliov, Leonas Valkunas, Roberta Croce*

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The light-harvesting complexes (LHCs) of plants can regulate the level of excitation in the photosynthetic membrane under fluctuating light by switching between different functional states with distinct fluorescence properties. One of the most fascinating yet obscure aspects of this regulation is how the vast conformational landscape of LHCs is modulated in different environments. Indeed, while in isolated antennae the highly fluorescent light-harvesting conformation dominates, LHC aggregates display strong fluorescence quenching, representing therefore a model system for the process of energy dissipation developed by plants to avoid photodamage in high light. This marked difference between the isolated and oligomeric conditions has led to the widespread belief that aggregation is the trigger for the photoprotective state of LHCs. Here, a detailed analysis of time-resolved fluorescence experiments performed on aggregates of CP29 - a minor LHC of plants - provides new insights into the heterogeneity of emissive states of this antenna. A comparison with the data on isolated CP29 reveals that, though aggregation can stabilize short-lived conformations to a certain extent, the massive quenching upon protein clustering is mainly achieved by energetic connectivity between complexes that maintain the same long-lived and dissipative states accessed in the isolated form. Our results also explain the typical far-red enhancement in the emission of antenna oligomers in terms of a sub-population of long-lived redshifted complexes competing with quenched complexes in the energy trapping. Finally, the role of selected chlorophylls in shaping the conformational landscape of the antenna is also addressed by studying mutants lacking specific pigments.

Original languageEnglish
Pages (from-to)5697-5709
Number of pages13
JournalChemical Science
Volume11
Issue number22
Early online date18 May 2020
DOIs
Publication statusPublished - 14 Jun 2020

Funding

We would like to thank Nicoletta Liguori and Sebastian Kemper for their assistance in the early stages of the experimental work and Pengqi Xu for purifying the CP29 complexes. Modelling was performed using the resources of the High Performance Computing Center “HPC Sauletekis” at Faculty of Physics, Vilnius University. This project was supported by the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 675006, by the Netherlands Organization for Scientic Research (NWO) via a Top grant (714.018.001) to R. C., and Gilibert project S-LZ-19-3 from the Research Council of Lithuania (A. G., J. C., L. V.).

FundersFunder number
Horizon 2020 Framework Programme
H2020 Marie Skłodowska-Curie Actions675006
Nederlandse Organisatie voor Wetenschappelijk OnderzoekS-LZ-19-3, 714.018.001
Lietuvos Mokslo Taryba
Horizon 2020

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