Deletion of psbJ leads to accumulation of Psb27–Psb28 photosystem II complexes in Thermosynechococcus elongatus

Abstract

The life cycle of Photosystem II (PSII) is embedded in a network of proteins that guides the complex through biogenesis, damage and repair. Some of these proteins, such as Psb27 and Psb28, are involved in cofactor assembly for which they are only transiently bound to the preassembled complex. In this work we isolated and analyzed PSII from a ΔpsbJ mutant of the thermophilic cyanobacterium Thermosynechococcus elongatus. From the four different PSII complexes that could be separated the most prominent one revealed a monomeric Psb27-Psb28 PSII complex with greatly diminished oxygen-evolving activity. The MALDI-ToF mass spectrometry analysis of intact low molecular weight subunits (<10kDa) depicted wild type PSII with the absence of PsbJ. Relative quantification of the PsbA1/PsbA3 ratio by LC-ESI mass spectrometry using (15)N labeled PsbA3-specific peptides indicated the complete replacement of PsbA1 by the stress copy PsbA3 in the mutant, even under standard growth conditions (50μmol photons m(-2) s(-1)). This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.

MS-based cross-linking analysis reveals the location of the PsbQ protein in cyanobacterial photosystem II

“…In contrast, loss of PsbV reduces the PsbQ level to nearly 40% of that in the WT cells (35). Our model is consistent with the experimental observation that PsbO is the first luminal extrinsic protein recruited to PSII (31,35). It is also supported by the earlier observation that deletion of the psbO gene abolishes the dimerization process of PSII in vivo (34), as observed in our PSII preparations as well (Fig.…”

“…5 B and C). In contrast, loss of PsbV reduces the PsbQ level to nearly 40% of that in the WT cells (35). Our model is consistent with the experimental observation that PsbO is the first luminal extrinsic protein recruited to PSII (31,35).…”

Mass spectrometry-based cross-linking study shows that the Psb28 protein binds to cytochrome b 559 in Photosystem II

“…This observation is consistent with the presence of Psb28 mainly in the RC47 complex (19)(20)(21)(22), to which CP43, and therefore Psb27, have not yet bound (12)(13)(14). Nowaczyk et al (32) detected both Psb27 and Psb28 in a subcomplex purified from the ΔpsbJ mutant of Thermosynechococcus elongatus. Absence of PsbJ may delay Psb28 dissociation, or this finding may be a result of subcomplex heterogeneity in the preparation.…”

“…A dimeric RC47 complex containing Psb28 was detected, however, in two previous studies (20,21). This complex may form during disassembly, similar to the dimeric Psb27-containing species (31), implying a role for Psb28 during disassembly, as previously proposed (20,32). The increased level of dimeric Psb28-containing complexes in our His47-PSII preparation compared with that in previous studies might have arisen from differences in the purification conditions.…”

Mass Spectrometry-based Footprinting Reveals Structural Dynamics of Loop E of the Chlorophyll-binding Protein CP43 during Photosystem II Assembly in the Cyanobacterium Synechocystis 6803

“…It is known that in the presence of Psb27, the binding stoichiometry of PsbO in PSII is less than that in active PSII (5,31). The partial dissociation of Psb27 in His27PSII may create the environment for partial PsbO binding.…”