Distinctive and functional pigment arrangements in Lhcp, a prasinophyte-specific light-harvesting complex

Light harvesting is essential for photosynthesis, and the diversity of light-harvesting systems has enabled photosynthetic organisms to acquire unique niches and thrive. Prasinophytes are marine green algae that branched off early in evolution and contain Lhcp as the primary light-harvesting complex. Lhcp is composed of proteins and pigments unique to prasinophytes but shares some structural and functional features with the plant-type light-harvesting complex LHCII. In this study, we used cryo-electron microscopy to determine the structure of Lhcp from the prasinophyte Ostreococcus tauri at 1.94 Å resolution, which revealed all the pigments responsible for light-harvesting function. Results show that the trimeric structure of Lhcp is stabilized by pigments, including a distinctive carotenoid, the cis -isomer of esterified antheraxanthin B. Comparing the structures and spectroscopic results of Lhcp and plant-type LHCII reveals how the cores of these two light-harvesting complexes are conserved and how structural differences support their functional divergence.