PXD068416

PXD068416 is an original dataset announced via ProteomeXchange.

Title	The molecular structure of Photosystem I from Chromera velia: A Mehler machine at 1.84 A resolution
Description	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, which occupies a unique evolutionary position between photosynthetic algae and parasitic apicomplexans, exhibits Photosystem I with highly unusual features. These include the splitting of the central PsaA subunit and the binding of superoxide dismutases as novel regular subunits. The organization of such a unique Photosystem I has remained enigmatic. Here, we present the cryo-EM structure of Chromera. velia Photosystem I at 1.84 Å resolution. Our analysis reveals a superoxide dismutase heterodimer bound to the stromal side of the core, stabilized by extensions of canonical subunits, two newly identified proteins (Psa34 and Psa35), and a reduced light-harvesting apparatus featuring a uniquely bound xanthophyll. We elucidate how the complex evolved to accommodate the superoxide dismutase, assemble the split PsaA subunit, and integrate antenna proteins in a non-canonical orientation. Based on our structural insights and prior physiological data, we propose that this specialized Photosystem I functions as an oxygen-photo-reduction 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. The high-resolution model presented here provides a foundation for future biotechnological applications aimed at optimizing photosynthetic design in diverse taxa.
HostingRepository	PRIDE
AnnounceDate	2026-01-02
AnnouncementXML	Submission_2026-01-02_05:59:05.771.xml
DigitalObjectIdentifier
ReviewLevel	Peer-reviewed dataset
DatasetOrigin	Original dataset
RepositorySupport	Unsupported dataset by repository
PrimarySubmitter	Tomáš Smrčka
SpeciesList	scientific name: Chromera velia; NCBI TaxID: NEWT:505693;
ModificationList	acetylated residue; monohydroxylated residue; complex glycosylation; deamidated residue; iodoacetamide derivatized residue
Instrument	timsTOF SCP

Revision	Datetime	Status	ChangeLog Entry
0	2025-09-16 07:55:05	ID requested
⏵ 1	2026-01-02 05:59:06	announced

10.1038/S41467-025-67637-0;

submitter keyword: Chromera velia, superoxide dismutase,photosystem I, N-glycosylation

Petr Man
contact affiliation	Institute of Microbiology of the Czech Academy of Sciences
contact email	pman@biomed.cas.cz
lab head
Tomáš Smrčka
contact affiliation	1) Institute of Microbiology of the Czech Academy of Sciences, Praha, 142 20, Czech Republic 2) Department of Biochemistry, Faculty of Science, Charles University, Praha, 128 00 Czech Republic
contact email	tomas.smrcka@biomed.cas.cz
dataset submitter

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PRIDE project URI

• PRIDE
  1. PXD068416
     1. Label: PRIDE project
     2. Name: The molecular structure of Photosystem I from Chromera velia: A Mehler machine at 1.84 A resolution