Optically detected magnetic resonance and mutational analysis reveal significant differences in the photochemistry and structure of chlorophyll f synthase and photosystem II

0583746 - BC 2024 RIV NL eng J - Journal Article
Agostini, Alessandro - Shen, G. - Bryant, D. A. - Golbeck, J. H. - van der Est, A. - Carbonera, D.
Optically detected magnetic resonance and mutational analysis reveal significant differences in the photochemistry and structure of chlorophyll f synthase and photosystem II.
Biochimica Et Biophysica Acta-Bioenergetics. Roč. 1864, č. 4 (2023), č. článku 149002. ISSN 0005-2728. E-ISSN 1879-2650
R&D Projects: GA MŠMT(CZ) EF18_053/0016982
Institutional support: RVO:60077344
Keywords : time-resolved epr * triplet-states * antenna complex * primary donor * oxygen * core * photosynthesis * spectrum * odmr * d1 * Chlorophyll f * Opticaly detected magnetic resonance * Triplet state * Type-II photosystem
OECD category: Biophysics
Impact factor: 4.3, year: 2022
Method of publishing: Open access
https://www.sciencedirect.com/science/article/pii/S0005272823000488?via%3Dihub

In cyanobacteria that undergo far red light photoacclimation (FaRLiP), chlorophyll (Chl) f is produced by the ChlF synthase enzyme, probably by photo-oxidation of Chl a. The enzyme forms homodimeric complexes and the primary amino acid sequence of ChlF shows a high degree of homology with the D1 subunit of photosystem II (PSII). However, few details of the photochemistry of ChlF are known. The results of a mutational analysis and optically detected magnetic resonance (ODMR) data from ChlF are presented. Both sets of data show that there are significant differences in the photochemistry of ChlF and PSII. Mutation of residues that would disrupt the donor side primary electron transfer pathway in PSII do not inhibit the production of Chl f, while alteration of the putative ChlZ, P680 and QA binding sites rendered ChlF non-functional. Together with previously published transient EPR and flash photolysis data, the ODMR data show that in untreated ChlF samples, the triplet state of P680 formed by intersystem crossing is the primary species generated by light excitation. This is in contrast to PSII, in which 3P680 is only formed by charge recombination when the quinone acceptors are removed or chemically reduced. The triplet states of a carotenoid (3Car) and a small amount of 3Chl f are also observed by ODMR. The polarization pattern of 3Car is consistent with its formation by triplet energy transfer from ChlZ if the carotenoid molecule is rotated by 15 degrees about its long axis compared to the orientation in PSII. It is proposed that the singlet oxygen formed by the interaction between molecular oxygen and 3P680 might be involved in the oxidation of Chl a to Chl f.
Permanent Link: https://hdl.handle.net/11104/0352306