Elucidating the structure of PSI-LHCI super complex from red alga Cyanidium caldarium and the molecular evolution of LHC

March 8, 2024

Researchers from Shizuoka University, Okayama University, the RIKEN Spring-8 Center, Tohoku University, and Kyoto University, along with those from the RIKEN CSRS, Toyohashi University of Technology, and others determined the structure of the photosystem-I light-harvesting complex-I (PSI-LHCI) derived from the red alga Cyanidium caldarium (C. caldarium) with a resolution of 1.92 angstroms by the single particle structural analysis using a cryo-electron microscope (CRYO ARM 300, JEOL). The obtained PSI-LHCI structure shows five LHCI subunits surrounding a PSI-monomer core.

Then, they focused on the red-lineage LHCI including that of C. caldarium, whose structure had already been determined, and suggested a LHCI evolution model based on the results from the molecular phylogenetic analysis. Research of LHC evolution has been conducted mainly by molecular phylogenetic analysis, although this approach alone would not be able to identify which LHC bonds to PSI.

This study identified the LHCI subunits bonding to PSI through structure analysis and performed phylogenetic analysis focusing only on these subunits. This approach has made it possible to understand the molecular evolution of red-lineage LHCI from a different perspective than ever.

Overall, combining structural and molecular phylogenetic analyses might produce new trends in research on the LHCI evolution.

Original article

Proceedings of the National Academy of Sciences of the United States of America
doi: 10.1073/pnas.2319658121

K. Kato, T. Hamaguchi, M. Kumazawa, Y. Nakajima, K. Ifuku, S. Hirooka, Y. Hirose, S. Miyagishima, T. Suzuki, K. Kawakami, N. Dohmae, K. Yonekura, J. Shen, R. Nagao,

"The structure of PSI-LHCI from Cyanidium caldarium provides evolutionary insights into conservation and diversity of red-lineage LHCs".

Contact

Naoshi Dohmae
Unit Leader
Biomolecular Characterization Unit