The monomeric photosystem I-light-harvesting antenna complex I (PSI-LHCI) supercomplex from the extremophilic red alga Cyanidioschyzon merolae represents an intermediate evolutionary link between the cyanobacterial PSI reaction center and its green algal/higher plant counterpart. We show that the C. merolae PSI-LHCI supercomplex is characterized by robustness in various extreme conditions. By a combination of biochemical, spectroscopic, mass spectrometry, and electron microscopy/single particle analyses, we dissected three molecular mechanisms underlying the inherent robustness of the C. merolae PSI-LHCI supercomplex: (1) the accumulation of photoprotective zeaxanthin in the LHCI antenna and the PSI reaction center; (2) structural remodeling of the LHCI antenna and adjustment of the effective absorption cross section; and (3) dynamic readjustment of the stoichiometry of the two PSI-LHCI isomers and changes in the oligomeric state of the PSI-LHCI supercomplex, accompanied by dissociation of the PsaK core subunit. We show that the largest low light-treated C. merolae PSI-LHCI supercomplex can bind up to eight Lhcr antenna subunits, which are organized as two rows on the PsaF/PsaJ side of the core complex. Under our experimental conditions, we found no evidence of functional coupling of the phycobilisomes with the PSI-LHCI supercomplex purified from various light conditions, suggesting that the putative association of this antenna with the PSI supercomplex is absent or may be lost during the purification procedure.

• MeSH
• biologická adaptace MeSH
• chlorofyl metabolismus   MeSH
• cirkulární dichroismus MeSH
• fluorescenční spektrometrie MeSH
• fotosystém I - proteinový komplex chemie   metabolismus   MeSH
• koncentrace vodíkových iontů MeSH
• molekulární evoluce MeSH
• Rhodophyta chemie   fyziologie   MeSH
• sinice chemie   fyziologie   MeSH
• světlo MeSH
• světlosběrné proteinové komplexy chemie   metabolismus   MeSH
• teplota MeSH
• zeaxanthiny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chlorofyl MeSH
• fotosystém I - proteinový komplex MeSH
• světlosběrné proteinové komplexy MeSH
• zeaxanthiny MeSH