Characterization of the psbK locus of Synechocystis sp. PCC 6803 in terms of Photosystem II function

Zhang, Z.-H.; Mayes, Steve R.; Vass, Imre; Nagy, László; Barber, James

doi:10.1007/bf00046763

Cited by 15 publications

(11 citation statements)

References 28 publications

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“…For example, null mutants of the Chlamydomonas psbH (36) and psbK (37) genes lead to a destabilization of the PSII core complex, reminiscent of the phenotype of the psbE null mutants presented here, whereas Synechocystis 6803 psbH (40) and psbK (41,42) null mutants assemble functional PSII and are still capable of photoautotrophy. The more drastic effect seen in the Chlamydomonas mutants is consistent with the presence of a more efficient proteolytic system in the chloroplast for the removal of mis-assembled PSII complexes.…”

Section: Discussionmentioning

confidence: 67%

The Chloroplast-encoded α Subunit of Cytochromeb-559 Is Required for Assembly of the Photosystem Two Complex in both the Light and the Dark in Chlamydomonas reinhardtii

Morais

Barber

Nixon

1998

Journal of Biological Chemistry

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The role of cytochrome b-559 in the photosystem two (PSII) complex has been investigated through the construction of a psbE null mutant by transformation of the chloroplast genome of the green alga Chlamydomonas reinhardtii. No PSII activity could be detected in this mutant either in oxygen evolution assays or by analysis of variable chlorophyll fluorescence. Immunoblotting experiments showed that the absence of PSII activity in the mutant was due to the loss of the PSII complex in both light-grown and dark-grown cultures. In contrast, the photosystem one reaction center polypeptide, PsaA, was present at wild-type levels in the mutant. RNA gel blot assays confirmed that the transcript levels for the psbA, psbD, and psbF genes were unaffected by disruption of the psbE gene, suggesting a post-transcriptional effect on their expression. Pulse-labeling experiments showed that either synthesis of PSII subunits was impaired in the psbE null mutant or there was extremely rapid degradation of newly synthesized subunits. Interestingly, the PsbE and PsbF subunits accumulated to wild-type levels in a psbA deletion mutant of C. reinhardtii, FuD7, which fails to synthesize D1 and assemble PSII. Our results provide evidence for a role for cytochrome b-559 in the early steps of assembly of the PSII complex, possibly as a redox-controlled nucleation factor that determines the level of PSII within the thylakoid membrane. Photosystem two (PSII)1 is a multisubunit complex within the thylakoid membrane that catalyzes the light-induced oxidation of water to molecular oxygen as well as the reduction of plastoquinone to plastoquinol (1). At the heart of PSII is a the reaction center (RC) complex composed of the polypeptides D1, D2, PsbI, and a transmembrane b-type cytochrome termed cytochrome b-559 (2). As yet, the function of this cytochrome within PSII is unresolved, but it probably plays a role in protecting the PSII RC from photoinactivation, possibly by acting as a source of electrons to reduce long-lived chlorophyll cation species within the PSII RC (3), which unless reduced would oxidize nearby amino acids within the protein complex (4).The structure of Cyt b-559 is quite unusual, as it is thought to be a heterodimer of two subunits arranged in parallel orientations: the ␣ subunit encoded by psbE and the ␤ subunit encoded by psbF (5). The haem molecule is likely to be ligated by the single histidine residues within each subunit (6). Although an ␣␤ heterodimeric structure for Cyt b-559 is generally favored, recent work has demonstrated that the genetic fusion of the N terminus of the ␤ subunit to the C terminus of the ␣ subunit in Synechocystis 6803 leads to the assembly of a functional cytochrome b-559 (7). Because the ␣␤ heterodimer model requires that the N termini of the monotopic ␣ and ␤ subunits lie on the same side of the membrane, the fusion of PsbE and PsbF without loss of PSII activity has been interpreted in terms of an ␣ 2 /␤ 2 homodimeric structure for Cyt b-559 with one haem bound to ␣ 2 and one to ␤ 2 (7). If this...

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Section: Discussionmentioning

confidence: 67%

The Chloroplast-encoded α Subunit of Cytochromeb-559 Is Required for Assembly of the Photosystem Two Complex in both the Light and the Dark in Chlamydomonas reinhardtii

Morais

Barber

Nixon

1998

Journal of Biological Chemistry

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“…PCC 6803 (Williams, 1988) referred to as the wild type. The following, previously described strains were used in the study: (1) the CP43-less strain, DCP43 (Vermaas et al, 1988); (2) the CP47 deletion strain, DCP47, in which the psbB gene is replaced by a spectinomycin-resistance cassette (EatonRye and Vermaas, 1991); (3) the PSI-less mutant DPSI, with both psaA and psaB replaced by chloramphenicol-resistance cassette (Shen et al, 1993) and its derivative lacking also the psbC gene (DCP43/DPSI); (4) the psbK deletion strain, DPsbK, in which the psbK gene is replaced by a kanamycin-resistance cassette (Zhang et al, 1993); (5) His-tagged strains accumulating unassembled CP47-His, unassembled CP47-His, and intact His-tagged PSII core complexes (PSII-His; Boehm et al, 2011); and (6) strain F-His expressing a His-tagged derivative of the PsaF subunit of PSI (Kubota et al, 2010).…”

Section: Construction and Cultivation Of Cyanobacterial Strainsmentioning

confidence: 99%

The Psb27 Assembly Factor Binds to the CP43 Complex of Photosystem II in the Cyanobacterium Synechocystis sp. PCC 6803

et al. 2011

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We have investigated the location of the Psb27 protein and its role in photosystem (PS) II biogenesis in the cyanobacterium Synechocystis sp. PCC 6803. Native gel electrophoresis revealed that Psb27 was present mainly in monomeric PSII core complexes but also in smaller amounts in dimeric PSII core complexes, in large PSII supercomplexes, and in the unassembled protein fraction. We conclude from analysis of assembly mutants and isolated histidine-tagged PSII subcomplexes that Psb27 associates with the "unassembled" CP43 complex, as well as with larger complexes containing CP43, possibly in the vicinity of the large lumenal loop connecting transmembrane helices 5 and 6 of CP43. A functional role for Psb27 in the biogenesis of CP43 is supported by the decreased accumulation and enhanced fragmentation of unassembled CP43 after inactivation of the psb27 gene in a mutant lacking CP47. Unexpectedly, in strains unable to assemble PSII, a small amount of Psb27 comigrated with monomeric and trimeric PSI complexes upon native gel electrophoresis, and Psb27 could be copurified with histidine-tagged PSI isolated from the wild type. Yeast two-hybrid assays suggested an interaction of Psb27 with the PsaB protein of PSI. Pulldown experiments also supported an interaction between CP43 and PSI. Deletion of psb27 did not have drastic effects on PSII assembly and repair but did compromise short-term acclimation to high light. The tentative interaction of Psb27 and CP43 with PSI raises the possibility that PSI might play a previously unrecognized role in the biogenesis/repair of PSII.

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“…The mature PsbX protein is reported to have a molecular mass of 4.1 kDa, and predicted to have a single transmembrane helix [73]. It has been detected in the oxygen‐evolving PSII core complex of higher plants and cyanobacteria [55,59] but is not contained in isolated RC preparations [72]. The deletion of the psb X gene in the cyanobacteria Synechocystis [74] and S. elongatus [75] did not inhibit PSII assembly and photoautotrophic growth.…”

Section: Lmw Subunitsmentioning

confidence: 99%

“…Deletion of the psbK gene in Synechocystis had very little e¡ect on photoautotrophic growth and PSII activity [54,55]. In the case of Chlamydomonas, however, the deletion of the gene destabilised the PSII complex and the transformant was unable to grow photoautotrophically [56].…”

Section: Psbkmentioning

confidence: 99%

Subunit positioning and transmembrane helix organisation in the core dimer of photosystem II

et al. 2001

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Recently 3D structural models of the photosystem II (PSII) core dimer complexes of higher plants (spinach) and cyanobacteria (Synechococcus elongatus) have been derived by electron ] crystallography respectively. The intermediate resolutions of these structures do not allow direct identification of side chains and therefore many of the individual subunits within the structure are unassigned. Here we review the structure of the higher plant PSII core dimer and provide evidence for the tentative assignment of the low molecular weight subunits. In so doing we highlight the similarities and differences between the higher plant and cyanobacterial structures. ß

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Characterization of the psbK locus of Synechocystis sp. PCC 6803 in terms of Photosystem II function

Cited by 15 publications

References 28 publications

The Chloroplast-encoded α Subunit of Cytochromeb-559 Is Required for Assembly of the Photosystem Two Complex in both the Light and the Dark in Chlamydomonas reinhardtii

The Chloroplast-encoded α Subunit of Cytochromeb-559 Is Required for Assembly of the Photosystem Two Complex in both the Light and the Dark in Chlamydomonas reinhardtii

The Psb27 Assembly Factor Binds to the CP43 Complex of Photosystem II in the Cyanobacterium Synechocystis sp. PCC 6803

Subunit positioning and transmembrane helix organisation in the core dimer of photosystem II

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