Poster De Conférence Année : 2024

Role of the of high-chlorophyll fluorescence 101 (HCF101), a chloroplastic Fe-S cluster transfer protein in the green microalga Chlamydomonas reinhardtii

Résumé

Iron-sulfur (Fe-S) proteins play a vital role in numerous chloroplastic processes, including photosynthesis and amino acid metabolism. The synthesis, transfer, and incorporation of Fe-S clusters into target proteins are orchestrated by the SUF (sulfur mobilization) machinery, involving approximately 20 proteins. The final step of Fe-S cluster transfer and insertion is executed by various proteins, including high-chlorophyll fluorescence 101 (HCF101), a P-loop NTPase. In Arabidopsis, hcf101 mutants exhibit a significant impact on photosystem I (PSI), consistent with the protein ability to bind a [4Fe-4S] cluster into a monomer in vitro. Three cysteine residues were initially proposed as essential for cluster binding, but two of them are not conserved in Chlamydomonas. To address this discrepancy, Chlamydomonas HCF101 was expressed as a recombinant protein in Escherichia coli and purified to homogeneity, confirming its ability to bind a [4Fe-4S] cluster. To gain further insights into HCF101 role in Chlamydomonas, a hcf101 mutant is currently under investigation, alongside a complemented strain. The mutant exhibited reduced maximal quantum yield of PSII in the dark (Fv/Fm), quantum yield of PSII in light-adapted cells (φPSII), and relative electron transfer rate of PSII (rETR). Additionally, the PSI/PSII ratio was decreased, and immunoblotting experiments indicated a significant impact on the abundance of [4Fe-4S] cluster-binding subunits of PSI. Growth measurements revealed that the doubling time was unaffected in minimal medium but significantly impacted in acetate medium, highlighting the photosynthetic deficiency in the hcf101 mutant strain when a carbon source is available. These findings collectively confirm the role of HCF101 in the maturation of [4Fe-4S] subunits of PSI in Chlamydomonas, and emphasize the need of further investigating the Fe-S cluster ligation mode.

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Dates et versions

hal-05318622 , version 1 (16-10-2025)

Identifiants

  • HAL Id : hal-05318622 , version 1

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Antoine Kairis, Anna Caccamo, Nicolas Rouhier, Claire Remacle. Role of the of high-chlorophyll fluorescence 101 (HCF101), a chloroplastic Fe-S cluster transfer protein in the green microalga Chlamydomonas reinhardtii. Iron Sulfur Proteins: Biogenesis, Regulation and Function meeting, Jun 2024, Winston Salem, United States. ⟨hal-05318622⟩
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