Yuan, X., Lukeš, M. orcid.org/0000-0003-3493-9780, Qian, P. orcid.org/0000-0002-5888-8546 et al. (9 more authors) (2025) The cryo-EM structure of Photosystem I from Chromera velia with a bound superoxide dismutase heterodimer. Nature Communications. ISSN: 2041-1723
Abstract
Photosystem I is a key component of the solar energy conversion machinery in oxygenic photosynthesis, and its core, where photochemistry occurs, is highly conserved. However, the coral-associated alga Chromera velia that is evolutionary linked to parasitic apicomplexans, exhibits Photosystem I with unusual features. These include the splitting of the central PsaA subunit and the binding of superoxide dismutases as regular subunits. The organization of such a unique Photosystem I was enigmatic. Here, we present the cryo-EM structure of Chromera velia Photosystem I at 1.84 Å resolution. Our work reveals a superoxide dismutase heterodimer bound to the stromal side of the core, stabilized by extensions of canonical subunits, a novel protein PsaV, and a reduced light-harvesting apparatus. We elucidate how the complex evolved to accommodate the superoxide dismutase, assemble the split PsaA, and integrate antenna proteins in a non-canonical orientation. Based on our data and prior physiological data, we propose that this specialized Photosystem I functions likely as an Mehler machine, redirecting electrons from Photosystem II back to water. This mechanism enables Chromera velia to manage redox imbalance and reduce photorespiration through localized oxygen consumption.
Metadata
| Item Type: | Article |
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| Authors/Creators: |
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| Copyright, Publisher and Additional Information: | © The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/. |
| Keywords: | Biochemistry and Cell Biology; Biological Sciences; Generic health relevance; Affordable and Clean Energy |
| Dates: |
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| Institution: | The University of Sheffield |
| Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Biosciences (Sheffield) |
| Date Deposited: | 08 Jan 2026 09:26 |
| Last Modified: | 08 Jan 2026 09:26 |
| Status: | Published online |
| Publisher: | Springer Science and Business Media LLC |
| Refereed: | Yes |
| Identification Number: | 10.1038/s41467-025-67637-0 |
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| Sustainable Development Goals: | |
| Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:236257 |
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