Conformational plasticity enables functional switching in diatom light-harvesting complexes.

Biomolecules exhibit a fundamental correlation between structure and function, which can be modulated by environmental factors. Deciphering this relationship remains a central and long-standing challenge for many protein families. In this study, we investigate such a correlation in the light-harvesting complexes (LHCs) of diatoms; unicellular, photosynthetic organisms that thrive in marine ecosystems. Using μs-long molecular dynamics simulations and machine learning, we reveal that all experimentally resolved LHC configurations correspond to a few distinct interconverting states linked to an intrinsic conformational transition that might affect the balance between light-harvesting and photoprotective modes; a property that can be tuned or engineered. Thus, to the best of our knowledge, we provide an original view on the plethora of experimentally resolved structures. Our model strongly correlates with experimental findings on the effect of the photoprotective protein LHCX1 and the xanthophyll cycle on the FCP acclimation states.