New paper on the conformational ensemble of CP29

Our paper on the mechanism of photoprotection in a light-harvesting complex is out on Nature Communications. In collaboration with the
MoLECoLab, we used enhanced-sampling MD, electronic calculations and cryo-EM data to analyze the conformational ensemble of CP29.

Cignoni, E. et al. A different perspective for nonphotochemical quenching in plant antenna complexes. Nat. Commun.12, 7152 (2021). 10.1038/s41467-021-27526-8

Light-harvesting complexes of plants exert a dual function of light-harvesting (LH) and photoprotection through processes collectively called nonphotochemical quenching (NPQ). While LH processes are relatively well characterized, those involved in NPQ are less understood. Here, we characterize the quenching mechanisms of CP29, a minor LHC of plants, through the integration of two complementary enhanced-sampling techniques, dimensionality reduction schemes, electronic calculations and the analysis of cryo-EM data in the light of the predicted conformational ensemble. Our study reveals that the switch between LH and quenching state is more complex than previously thought. Several conformations of the lumenal side of the protein occur and differently affect the pigments’ relative geometries and interactions. Moreover, we show that a quenching mechanism localized on a single chlorophyll-carotenoid pair is not sufficient but many chlorophylls are simultaneously involved. In such a diffuse mechanism, short-range interactions between each carotenoid and different chlorophylls combined with a protein-mediated tuning of the carotenoid excitation energies have to be considered in addition to the commonly suggested Coulomb interactions.