Xiaochun Qin and colleagues have provided a high-resolution crystal structure of a plant protein supercomplex critical to photosynthesis, shedding new light on how this extremely effective solar energy converter achieves its impressive performance.

The photosynthesis of many plants relies upon the large light-harvesting complex I (LHC1), which surrounds photosystem I (PSI) and captures sunlight. LHC1 is able to transfer the energy it absorbs to the PSI core, where it is converted into chemical energy with close to 100% efficiency.

Previous studies have solved the structure of PSI-LHC1 in the pea plant, Pisum satirvum, at low resolution, revealing the presence of certain pigments and proteins. But Qin et al. now provide more detail with a 2.8 angstrom-resolution structure that shows how such cofactors are arranged and organized.

Their findings highlight the orientation of specific pigments, such as chlorophylls and carotenoids, during several key energy-transfer interactions.

Taken together, they provide a structural basis for understanding the photosynthetic mechanisms involved in harvesting light from the sun and protecting plant cells from its harmful effects. A Perspective article by Roberta Croce explains these results and their implications in greater detail.