PXD079525

PXD079525 is an original dataset announced via ProteomeXchange.

Title	Chemical crosslinking of photosynthetic protein complexes in Cyanidioschyzon merolae
Description	Efficient photosynthetic electron transfer relies on transient interactions between photosystem I (PSI) and soluble electron carriers. However, structural information describing these transient interactions are limited in red algae. Here, we applied chemical crosslinking mass spectrometry (XL-MS) to isolated thylakoid membranes of the red alga Cyanidioschyzon merolae and generated an interactome map of photosynthetic protein complexes. Using three independent crosslink identification algorithms, we obtained a high-confidence dataset of intra/inter-complex interactions. Among them, we identified a crosslink between K94 of FNR and K108 of the stromal subunit PsaD. Crosslinking restraint-guided protein-protein docking using HADDOCK2.4 revealed a direct docking interface for FNR on PsaD side. Structural analysis of the resulting complex indicated that the binding of FNR to PSI is predominantly electrostatic, in which the K4 residue of FNR is involved in making a salt bridge with E91 of PsaD as well as a conventional hydrogen bond with G90 of PsaD. Site-directed mutagenesis of the FNR K4 residue significantly impaired the NADP⁺ reduction kinetics, as compared to the WT FNR, supporting that FNR binding to PSI is required for efficient FNR and ferredoxin (FDX) dependent NADP+ photoreduction. These results strongly suggest that FNR binds to the stromal side of PSI in an orientation that enables efficient electron transfer from FDX. Additionally, we detected a crosslink between the phycobilisome core protein ApcA and PsaD suggesting that it may serve as a shared interaction hub for both FNR and PBS, implying that these interactions could either occur simultaneously or compete for binding while still allowing electron transfer via soluble FDX.
HostingRepository	PRIDE
AnnounceDate	2026-08-06
AnnouncementXML	Submission_2026-08-06_02:14:47.839.xml
DigitalObjectIdentifier
ReviewLevel	Peer-reviewed dataset
DatasetOrigin	Original dataset
RepositorySupport	Unsupported dataset by repository
PrimarySubmitter	Martin Scholz
SpeciesList	scientific name: Cyanidioschyzon merolae; NCBI TaxID: NEWT:45157;
ModificationList	crosslinked residues; acetylated residue; monohydroxylated residue; iodoacetamide derivatized residue
Instrument	Q Exactive Plus

Revision	Datetime	Status	ChangeLog Entry
0	2026-06-10 08:14:34	ID requested
⏵ 1	2026-08-06 02:14:48	announced

10.1111/TPJ.71017;

submitter keyword: Cyanidioschyzon merolae, Photosystem I, FNR, DSS, crosslinking

Michael Hippler
contact affiliation	Uni Muenster/IBBP
contact email	mhippler@uni-muenster.de
lab head
Martin Scholz
contact affiliation	IBBP Muenster
contact email	mscholz@uni-muenster.de
dataset submitter

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PRIDE project URI

• PRIDE
  1. PXD079525
     1. Label: PRIDE project
     2. Name: Chemical crosslinking of photosynthetic protein complexes in Cyanidioschyzon merolae