Nejvíce citovaný článek - PubMed ID 30107031
Plant and algal chlorophyll synthases function in Synechocystis and interact with the YidC/Alb3 membrane insertase
The biogenesis of Photosystem II is a complicated process requiring numerous auxiliary factors to assist in all steps of its assembly. The cyanobacterial protein Ycf39 forms a stress-induced complex with 2 small chlorophyll-binding, High-light-inducible proteins C and D (HliC and HliD), and has been reported to participate in the insertion of chlorophyll molecules into the central D1 subunit of Photosystem II. However, how this process is organized remains unknown. Here, we show that Ycf39 and both HliC and HliD can form distinct complexes with chlorophyll synthase (ChlG) in the model cyanobacterium Synechocystis sp. PCC 6803. We isolated and characterized ChlG complexes from various strains grown under different conditions and provide a mechanistic view of the docking of Ycf39 to ChlG via HliD and the structural role of HliC. In the absence of stress, chlorophyll is produced by the ChlG-HliD2-ChlG complex, which is stabilized by chlorophyll and zeaxanthin molecules bound to the HliD homodimer. The switch to high light leads to stress pressure and greatly elevated synthesis of HliC, resulting in the replacement of HliD homodimers with HliC-HliD heterodimers. Unlike HliD, HliC cannot interact directly with ChlG or Ycf39. Therefore, the original ChlG-HliD2-ChlG complex is converted into a ChlG-HliD-HliC hetero-trimer that presumably binds transiently to Ycf39 and the nascent D1 polypeptide. We speculate that this molecular machinery promotes the delivery of chlorophyll to D1 upon high-light-induced chlorophyll deficiency. The HliD homodimers formed under standard, nonstress growth conditions and attached to ChlG could serve as an emergency chlorophyll reserve.
- MeSH
- bakteriální proteiny * metabolismus genetika MeSH
- chlorofyl metabolismus MeSH
- fotosystém II (proteinový komplex) * metabolismus MeSH
- ligasy tvořící vazby C-O * metabolismus genetika MeSH
- světlo * MeSH
- Synechocystis * metabolismus účinky záření genetika MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- bakteriální proteiny * MeSH
- chlorofyl MeSH
- chlorophyll synthetase MeSH Prohlížeč
- fotosystém II (proteinový komplex) * MeSH
- high light-inducible protein, cyanobacteria MeSH Prohlížeč
- ligasy tvořící vazby C-O * MeSH
- světlosběrné proteinové komplexy MeSH
The growth of plants, algae, and cyanobacteria relies on the catalytic activity of the oxygen-evolving PSII complex, which uses solar energy to extract electrons from water to feed into the photosynthetic electron transport chain. PSII is proving to be an excellent system to study how large multi-subunit membrane-protein complexes are assembled in the thylakoid membrane and subsequently repaired in response to photooxidative damage. Here we summarize recent developments in understanding the biogenesis of PSII, with an emphasis on recent insights obtained from biochemical and structural analysis of cyanobacterial PSII assembly/repair intermediates. We also discuss how chlorophyll synthesis is synchronized with protein synthesis and suggest a possible role for PSI in PSII assembly. Special attention is paid to unresolved and controversial issues that could be addressed in future research.
