Epigenetic DNA modifications are pivotal in eukaryotic gene expression, but their regulatory significance in bacteria is less understood. In Synechocystis 6803, the DNA methyltransferase M.Ssp6803II modifies the first cytosine in the GGCC motif, forming N4-methylcytosine (GGm4CC). Deletion of the sll0729 gene encoding M.Ssp6803II (∆sll0729) caused a bluish phenotype due to reduced chlorophyll levels, which was reversed by suppressor mutations. Re-sequencing of 7 suppressor clones revealed a common GGCC to GGTC mutation in the slr1790 promoter's discriminator sequence, encoding protoporphyrinogen IX oxidase, HemJ, crucial for tetrapyrrole biosynthesis. Transcriptomic and qPCR analyses indicated aberrant slr1790 expression in ∆sll0729 mutants. This aberration led to the accumulation of coproporphyrin III and protoporphyrin IX, indicative of impaired HemJ activity. To confirm the importance of DNA methylation in hemJ expression, hemJ promoter variants with varying discriminator sequences were introduced into the wild type, followed by sll0729 deletion. The sll0729 deletion segregated in strains with the GGTC discriminator motif, resulting in wild-type-like pigmentation, whereas freshly prepared ∆sll0729 mutants with the native hemJ promoter exhibited the bluish phenotype. These findings demonstrate that hemJ is tightly regulated in Synechocystis and that N4-methylcytosine is essential for proper hemJ expression. Thus, cytosine N4-methylation is a relevant epigenetic marker in Synechocystis and likely other cyanobacteria.

• Klíčová slova
• DNA methyltransferase, HemJ, cyanobacteria, epigenetic modifications, tetrapyrrole biosynthesis,
• MeSH
• bakteriální proteiny metabolismus   genetika   MeSH
• epigeneze genetická * MeSH
• metylace DNA * MeSH
• mutace MeSH
• promotorové oblasti (genetika) * MeSH
• regulace genové exprese u bakterií MeSH
• Synechocystis * genetika   metabolismus   MeSH
• tetrapyrroly * metabolismus   biosyntéza   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• bakteriální proteiny MeSH
• tetrapyrroly * MeSH

FtsH proteases (FtsHs) belong to intramembrane ATP-dependent metalloproteases which are widely distributed in eubacteria, mitochondria and chloroplasts. The best-studied roles of FtsH in Escherichia coli include quality control of membrane proteins, regulation of response to heat shock, superoxide stress and viral infection, and control of lipopolysaccharide biosynthesis. While heterotrophic bacteria mostly contain a single indispensable FtsH complex, photosynthetic cyanobacteria usually contain three FtsH complexes: two heterocomplexes and one homocomplex. The essential cytoplasmic FtsH1/3 most probably fulfills a role similar to other bacterial FtsHs, whereas the thylakoid FtsH2/3 heterocomplex and FtsH4 homocomplex appear to maintain the photosynthetic apparatus of cyanobacteria and optimize its functionality. Moreover, recent studies suggest the involvement of all FtsH proteases in a complex response to nutrient stresses. In this review, we aim to comprehensively evaluate the functions of the cyanobacterial FtsHs specifically under stress conditions with emphasis on nutrient deficiency and high irradiance. We also point to various unresolved issues concerning FtsH functions, which deserve further attention.

• Klíčová slova
• Cyanobacteria, FtsH, Nutrient stress, Photodamage, Photosystem,
• MeSH
• bakteriální proteiny * metabolismus   genetika   MeSH
• fyziologický stres * MeSH
• proteasy závislé na ATP metabolismus   genetika   MeSH
• sinice * metabolismus   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• bakteriální proteiny * MeSH
• proteasy závislé na ATP MeSH

FtsH proteases are membrane-embedded proteolytic complexes important for protein quality control and regulation of various physiological processes in bacteria, mitochondria, and chloroplasts. Like most cyanobacteria, the model species Synechocystis sp. PCC 6803 contains four FtsH homologs, FtsH1-FtsH4. FtsH1-FtsH3 form two hetero-oligomeric complexes, FtsH1/3 and FtsH2/3, which play a pivotal role in acclimation to nutrient deficiency and photosystem II quality control, respectively. FtsH4 differs from the other three homologs by the formation of a homo-oligomeric complex, and together with Arabidopsis thaliana AtFtsH7/9 orthologs, it has been assigned to another phylogenetic group of unknown function. Our results exclude the possibility that Synechocystis FtsH4 structurally or functionally substitutes for the missing or non-functional FtsH2 subunit in the FtsH2/3 complex. Instead, we demonstrate that FtsH4 is involved in the biogenesis of photosystem II by dual regulation of high light-inducible proteins (Hlips). FtsH4 positively regulates expression of Hlips shortly after high light exposure but is also responsible for Hlip removal under conditions when their elevated levels are no longer needed. We provide experimental support for Hlips as proteolytic substrates of FtsH4. Fluorescent labeling of FtsH4 enabled us to assess its localization using advanced microscopic techniques. Results show that FtsH4 complexes are concentrated in well-defined membrane regions at the inner and outer periphery of the thylakoid system. Based on the identification of proteins that co-purified with the tagged FtsH4, we speculate that FtsH4 concentrates in special compartments in which the biogenesis of photosynthetic complexes takes place.

• Klíčová slova
• FtsH4, high light-inducible protein, photosystem II biogenesis, proteolysis, thylakoid,
• MeSH
• Arabidopsis * genetika   metabolismus   MeSH
• chloroplasty metabolismus   MeSH
• fotosystém II (proteinový komplex) genetika   metabolismus   MeSH
• fylogeneze MeSH
• metaloproteasy genetika   metabolismus   MeSH
• proteasy MeSH
• proteiny huseníčku * genetika   metabolismus   MeSH
• Synechocystis * genetika   metabolismus   MeSH
• tylakoidy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fotosystém II (proteinový komplex) MeSH
• FtsH4 protein, Arabidopsis MeSH Prohlížeč
• metaloproteasy MeSH
• proteasy MeSH
• proteiny huseníčku * MeSH

Type IV pili are bacterial surface-exposed filaments that are built up by small monomers called pilin proteins. Pilins are synthesized as longer precursors (prepilins), the N-terminal signal peptide of which must be removed by the processing protease PilD. A mutant of the cyanobacterium Synechocystis sp. PCC 6803 lacking the PilD protease is not capable of photoautotrophic growth because of the impaired function of Sec translocons. Here, we isolated phototrophic suppressor strains of the original ΔpilD mutant and, by sequencing their genomes, identified secondary mutations in the SigF sigma factor, the γ subunit of RNA polymerase, the signal peptide of major pilin PilA1, and in the pilA1-pilA2 intergenic region. Characterization of suppressor strains suggests that, rather than the total prepilin level in the cell, the presence of non-glycosylated PilA1 prepilin is specifically harmful. We propose that the restricted lateral mobility of the non-glycosylated PilA1 prepilin causes its accumulation in the translocon-rich membrane domains, which attenuates the synthesis of membrane proteins.

• Klíčová slova
• PilD peptidase, Synechocystis, Type IV pili, photosystem II, suppressor mutations,
• Publikační typ
• časopisecké články MeSH

The membrane-embedded FtsH proteases found in bacteria, chloroplasts, and mitochondria are involved in diverse cellular processes including protein quality control and regulation. The genome of the model cyanobacterium Synechocystis sp PCC 6803 encodes four FtsH homologs designated FtsH1 to FtsH4. The FtsH3 homolog is present in two hetero-oligomeric complexes: FtsH2/3, which is responsible for photosystem II quality control, and the essential FtsH1/3 complex, which helps maintain Fe homeostasis by regulating the level of the transcription factor Fur. To gain a more comprehensive insight into the physiological roles of FtsH hetero-complexes, we performed genome-wide expression profiling and global proteomic analyses of Synechocystis mutants conditionally depleted of FtsH3 or FtsH1 grown under various nutrient conditions. We show that the lack of FtsH1/3 leads to a drastic reduction in the transcriptional response to nutrient stress of not only Fur but also the Pho, NdhR, and NtcA regulons. In addition, this effect is accompanied by the accumulation of the respective transcription factors. Thus, the FtsH1/3 complex is of critical importance for acclimation to iron, phosphate, carbon, and nitrogen starvation in Synechocystis.plantcell;31/12/2912/FX1F1fx1.

• MeSH
• aklimatizace genetika   MeSH
• bakteriální proteiny genetika   metabolismus   MeSH
• dusík nedostatek   metabolismus   MeSH
• exprese genu MeSH
• fosfáty nedostatek   metabolismus   MeSH
• fosforylace MeSH
• fotosystém II (proteinový komplex) chemie   genetika   metabolismus   MeSH
• metaloproteasy genetika   metabolismus   MeSH
• mutace MeSH
• proteiny vázající fosfáty genetika   metabolismus   MeSH
• proteolýza MeSH
• proteom genetika   metabolismus   MeSH
• proteomika MeSH
• regulace genové exprese u bakterií genetika   MeSH
• regulon genetika   MeSH
• represorové proteiny genetika   metabolismus   MeSH
• ribozomální proteiny genetika   metabolismus   MeSH
• Synechocystis enzymologie   metabolismus   MeSH
• transkripční faktory genetika   metabolismus   MeSH
• uhlík nedostatek   metabolismus   MeSH
• živiny nedostatek   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriální proteiny MeSH
• dusík MeSH
• ferric uptake regulating proteins, bacterial MeSH Prohlížeč
• fosfáty MeSH
• fotosystém II (proteinový komplex) MeSH
• metaloproteasy MeSH
• proteiny vázající fosfáty MeSH
• proteom MeSH
• represorové proteiny MeSH
• ribozomální proteiny MeSH
• transkripční faktory MeSH
• uhlík MeSH

Oxygenic photosynthesis relies on accessory factors to promote the assembly and maintenance of the photosynthetic apparatus in the thylakoid membranes. The highly conserved membrane-bound rubredoxin-like protein RubA has previously been implicated in the accumulation of both PSI and PSII, but its mode of action remains unclear. Here, we show that RubA in the cyanobacterium Synechocystis sp PCC 6803 is required for photoautotrophic growth in fluctuating light and acts early in PSII biogenesis by promoting the formation of the heterodimeric D1/D2 reaction center complex, the site of primary photochemistry. We find that RubA, like the accessory factor Ycf48, is a component of the initial D1 assembly module as well as larger PSII assembly intermediates and that the redox-responsive rubredoxin-like domain is located on the cytoplasmic surface of PSII complexes. Fusion of RubA to Ycf48 still permits normal PSII assembly, suggesting a spatiotemporal proximity of both proteins during their action. RubA is also important for the accumulation of PSI, but this is an indirect effect stemming from the downregulation of light-dependent chlorophyll biosynthesis induced by PSII deficiency. Overall, our data support the involvement of RubA in the redox control of PSII biogenesis.

• MeSH
• bakteriální proteiny genetika   metabolismus   MeSH
• biologické pigmenty izolace a purifikace   MeSH
• chlorofyl biosyntéza   MeSH
• fotosyntéza fyziologie   MeSH
• fotosystém I (proteinový komplex) metabolismus   MeSH
• fotosystém II (proteinový komplex) metabolismus   MeSH
• mutace MeSH
• rubredoxiny chemie   genetika   metabolismus   MeSH
• Synechocystis genetika   růst a vývoj   metabolismus   MeSH
• tylakoidy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriální proteiny MeSH
• biologické pigmenty MeSH
• chlorofyl MeSH
• fotosystém I (proteinový komplex) MeSH
• fotosystém II (proteinový komplex) MeSH
• rubredoxiny MeSH

Cyanobacteria possess a family of one-helix high-light-inducible proteins (HLIPs) that are widely viewed as ancestors of the light-harvesting antenna of plants and algae. HLIPs are essential for viability under various stress conditions, although their exact role is not fully understood. The unicellular cyanobacterium Synechocystis sp. PCC 6803 contains four HLIPs named HliA-D, and HliD has recently been isolated in a small protein complex and shown to bind chlorophyll and β-carotene. However, no HLIP has been isolated and characterized in a pure form up to now. We have developed a protocol to purify large quantities of His-tagged HliC from an engineered Synechocystis strain. Purified His-HliC is a pigmented homo-oligomer and is associated with chlorophyll and β-carotene with a 2:1 ratio. This differs from the 3:1 ratio reported for HliD. Comparison of these two HLIPs by resonance Raman spectroscopy revealed a similar conformation for their bound β-carotenes, but clear differences in their chlorophylls. We present and discuss a structural model of HliC, in which a dimeric protein binds four chlorophyll molecules and two β-carotenes.

• Klíčová slova
• Chlorophyll, HLIPs, HliC, Raman spectroscopy, Synechocystis, β-Carotene,
• MeSH
• bakteriální proteiny chemie   genetika   izolace a purifikace   metabolismus   MeSH
• beta-karoten metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• multimerizace proteinu MeSH
• Ramanova spektroskopie MeSH
• rekombinantní proteiny genetika   izolace a purifikace   metabolismus   MeSH
• světlosběrné proteinové komplexy genetika   metabolismus   MeSH
• Synechocystis genetika   metabolismus   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• bakteriální proteiny MeSH
• beta-karoten MeSH
• chlorofyl MeSH
• high light-inducible protein, cyanobacteria MeSH Prohlížeč
• rekombinantní proteiny MeSH
• světlosběrné proteinové komplexy MeSH

Photosystem II (PSII) is a large enzyme complex embedded in the thylakoid membrane of oxygenic phototrophs. The biogenesis of PSII requires the assembly of more than 30 subunits, with the assistance of a number of auxiliary proteins. In plants and cyanobacteria, the photosynthesis-affected mutant 68 (Pam68) is important for PSII assembly. However, its mechanisms of action remain unknown. Using a Synechocystis PCC 6803 strain expressing Flag-tagged Pam68, we purified a large protein complex containing ribosomes, SecY translocase, and the chlorophyll-binding PSII inner antenna CP47. Using 2D gel electrophoresis, we identified a pigmented Pam68-CP47 subcomplex and found Pam68 bound to ribosomes. Our results show that Pam68 binds to ribosomes even in the absence of CP47 translation. Furthermore, Pam68 associates with CP47 at an early phase of its biogenesis and promotes the synthesis of this chlorophyll-binding polypeptide until the attachment of the small PSII subunit PsbH. Deletion of both Pam68 and PsbH nearly abolishes the synthesis of CP47, which can be restored by enhancing chlorophyll biosynthesis. These results strongly suggest that ribosome-bound Pam68 stabilizes membrane segments of CP47 and facilitates the insertion of chlorophyll molecules into the translated CP47 polypeptide chain.

• MeSH
• 2D gelová elektroforéza MeSH
• bakteriální proteiny genetika   metabolismus   MeSH
• buněčná membrána metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• fosfoproteiny genetika   metabolismus   MeSH
• fotosystém II (proteinový komplex) genetika   metabolismus   MeSH
• mutace MeSH
• ribozomy metabolismus   MeSH
• světlosběrné proteinové komplexy genetika   metabolismus   MeSH
• Synechocystis genetika   metabolismus   MeSH
• vazba proteinů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bakteriální proteiny MeSH
• chlorofyl MeSH
• fosfoproteiny MeSH
• fotosystém II (proteinový komplex) MeSH
• photosystem II, chlorophyll-binding protein, CP-47 MeSH Prohlížeč
• photosystem II, psbH subunit MeSH Prohlížeč
• světlosběrné proteinové komplexy MeSH