Properties of Photosystem II Lacking the PsbJ Subunit
Overview
Affiliations
Photosystem II (PSII), the oxygen-evolving enzyme, consists of 17 trans-membrane and 3 extrinsic membrane proteins. Other subunits bind to PSII during assembly, like Psb27, Psb28, and Tsl0063. The presence of Psb27 has been proposed (Zabret et al. in Nat Plants 7:524-538, 2021; Huang et al. Proc Natl Acad Sci USA 118:e2018053118, 2021; Xiao et al. in Nat Plants 7:1132-1142, 2021) to prevent the binding of PsbJ, a single transmembrane α-helix close to the quinone Q binding site. Consequently, a PSII rid of Psb27, Psb28, and Tsl0034 prior to the binding of PsbJ would logically correspond to an assembly intermediate. The present work describes experiments aiming at further characterizing such a ∆PsbJ-PSII, purified from the thermophilic Thermosynechococcus elongatus, by means of MALDI-TOF spectroscopy, thermoluminescence, EPR spectroscopy, and UV-visible time-resolved spectroscopy. In the purified ∆PsbJ-PSII, an active MnCaO cluster is present in 60-70% of the centers. In these centers, although the forward electron transfer seems not affected, the Em of the Q/Q couple increases by ≥ 120 mV , thus disfavoring the electron coming back on Q. The increase of the energy gap between Q/Q and Q/Q could contribute in a protection against the charge recombination between the donor side and Q, identified at the origin of photoinhibition under low light (Keren et al. in Proc Natl Acad Sci USA 94:1579-1584, 1997), and possibly during the slow photoactivation process.
Boussac A, Selles J, Sugiura M Photosynth Res. 2025; 163(1):5.
PMID: 39810006 DOI: 10.1007/s11120-024-01131-4.
Structural basis for an early stage of the photosystem II repair cycle in Chlamydomonas reinhardtii.
Li A, You T, Pang X, Wang Y, Tian L, Li X Nat Commun. 2024; 15(1):5211.
PMID: 38890314 PMC: 11189392. DOI: 10.1038/s41467-024-49532-2.
Thermophilic cyanobacteria-exciting, yet challenging biotechnological chassis.
Rasul F, You D, Jiang Y, Liu X, Daroch M Appl Microbiol Biotechnol. 2024; 108(1):270.
PMID: 38512481 PMC: 10957709. DOI: 10.1007/s00253-024-13082-w.
Structure of a unique PSII-Pcb tetrameric megacomplex in a chlorophyll -containing cyanobacterium.
Shen L, Gao Y, Tang K, Qi R, Fu L, Chen J Sci Adv. 2024; 10(8):eadk7140.
PMID: 38394197 PMC: 10889353. DOI: 10.1126/sciadv.adk7140.
Binding and functions of the two chloride ions in the oxygen-evolving center of photosystem II.
Imaizumi K, Ifuku K Photosynth Res. 2022; 153(3):135-156.
PMID: 35698013 DOI: 10.1007/s11120-022-00921-y.