Disentangling protein and lipid interactions that control a molecular switch in photosynthetic light harvesting

Emanuela Crisafi, Anjali Pandit
Leiden Institute of Chemistry, Einsteinweg 55 2333 CC Leiden, The Netherlands

Photosynthetic light-harvesting antennae (LHCII) form supra-molecular arrays with strong connectivity that capture sunlight and transfer the excitations over long distances towards the photosynthetic reaction centers. This structures are dynamic assemblies that continuously adapt to the light conditions for prevention of photo damage.

Concerning the dynamicity of this protein, we propose a comparison in terms of structure and fluorescence properties of LHCII inserted in membrane models to investigate the LHCII mechanistic functional switch. The LHCII pigment-protein complexes are unique in possessing chlorophylls (Chls) and xanthophylls at their peripheral sites that form intrinsic probes, reporting changes in the microenvironment. By adjusting the protein to lipid ratio in the proteoliposomes, we determine the onset ratio for protein aggregation in membranes, bridging the gap between properties of isolated proteins and of their aggregated states. In line with the conclusions from Akhtar et al[1].

We observe that excitonic CD spectra are sensitive to changes in the LHCII microenvironment, not per se correlated with fluorescence quenching.

Reference

[1] Journal of biological chemistry 2015, 290, 4877