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The Photosystem II Assembly Factor Ycf48 from the Cyanobacterium Synechocystis sp. PCC 6803 Is Lipidated Using an Atypical Lipobox Sequence.

ABSTRACT: Photochemical energy conversion during oxygenic photosynthesis is performed by membrane-embedded chlorophyll-binding protein complexes. The biogenesis and maintenance of these complexes requires auxiliary protein factors that optimize the assembly process and protect nascent complexes from photodamage. In cyanobacteria, several lipoproteins contribute to the biogenesis and function of the photosystem II (PSII) complex. They include CyanoP, CyanoQ, and Psb27, which are all attached to the lumenal side of PSII complexes. Here, we show that the lumenal Ycf48 assembly factor found in the cyanobacterium Synechocystis sp. PCC 6803 is also a lipoprotein. Detailed mass spectrometric analysis of the isolated protein supported by site-directed mutagenesis experiments indicates lipidation of the N-terminal C29 residue of Ycf48 and removal of three amino acids from the C-terminus. The lipobox sequence in Ycf48 contains a cysteine residue at the -3 position compared to Leu/Val/Ile residues found in the canonical lipobox sequence. The atypical Ycf48 lipobox sequence is present in most cyanobacteria but is absent in eukaryotes. A possible role for lipoproteins in the coordinated assembly of cyanobacterial PSII is discussed.

SUBMITTER: Knoppova J

PROVIDER: S-EPMC8038367 | biostudies-literature |

REPOSITORIES: biostudies-literature

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High-resolution cryo-electron microscopy structure of photosystem II from the mesophilic cyanobacterium, Synechocystis sp. PCC 6803.

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Project description:Small CAB-like proteins (SCPs) are single-helix light-harvesting-like proteins found in all organisms performing oxygenic photosynthesis. We investigated the function of these stress-induced proteins in the cyanobacterium Synechocystis sp. PCC 6803 by comparing a strain, which expresses SCPs constitutively, with a mutant lacking all five SCPs. In the absence of SCPs, cells were larger, and showed irregular thylakoid structure and cell-surfaces. Deletion of scp genes strongly affected the carbon-nitrogen balance, causing accumulation of carbohydrates and a decrease in N-rich compounds (proteins and chlorophyll a). Data from transcriptomic and metabolomic experiments demonstrated that SCPs mediated stabilization of chlorophyll a under stress conditions is crucial to maintain the C/N balance. SCPs diminished the formation of reactive oxygen species, preventing cellular damage by adjusting the de-novo production of chlorophyll a to demand levels. Lack of SCP expression under stress conditions had a large impact on the metabolism of the entire cell. Synechocystis 6803 PSI-less (Shen et al 1993) and PSI-less/ScpABCDE- (Xu et al 2004) mutants were cultivated at 30°C at a light intensity of 4–5 μmol photons m–2 s–1 in BG-11 growth medium (Rippka et al 1979) supplemented with 10 mM glucose. Cells (40–50 ml) from both control and the mutant cultures were collected at mid-log phase by rapid filtration (Pall Supor 800 Filter, 0.8 mm) and total RNA extracted after Pinto et al. (Pinto et al 2009). Single-stranded cDNA preparation, labelling, and hybridization onto the microarray slides were performed after Eisenhut et al. (2007). The microarray slides were scanned with an Agilent Microarray Scanner (model G2505B) with default settings.

2015-03-30 | E-GEOD-59371 | biostudies-arrayexpress

The Role of Slr0151, a Tetratricopeptide Repeat Protein from Synechocystis sp. PCC 6803, during Photosystem II Assembly and Repair.

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Project description:Biochemical characterization of intermediates involved in the assembly of the oxygen-evolving Photosystem II (PSII) complex is hampered by their low abundance in the membrane. Using the cyanobacterium Synechocystis sp. PCC 6803, we describe here the isolation of the CP47 and CP43 subunits, which, during biogenesis, attach to a reaction center assembly complex containing D1, D2, and cytochrome b(559), with CP47 binding first. Our experimental approach involved a combination of His tagging, the use of a D1 deletion mutant that blocks PSII assembly at an early stage, and, in the case of CP47, the additional inactivation of the FtsH2 protease involved in degrading unassembled PSII proteins. Absorption spectroscopy and pigment analyses revealed that both CP47-His and CP43-His bind chlorophyll a and β-carotene. A comparison of the low temperature absorption and fluorescence spectra in the Q(Y) region for CP47-His and CP43-His with those for CP47 and CP43 isolated by fragmentation of spinach PSII core complexes confirmed that the spectroscopic properties are similar but not identical. The measured fluorescence quantum yield was generally lower for the proteins isolated from Synechocystis sp. PCC 6803, and a 1-3-nm blue shift and a 2-nm red shift of the 77 K emission maximum could be observed for CP47-His and CP43-His, respectively. Immunoblotting and mass spectrometry revealed the co-purification of PsbH, PsbL, and PsbT with CP47-His and of PsbK and Psb30/Ycf12 with CP43-His. Overall, our data support the view that CP47 and CP43 form preassembled pigment-protein complexes in vivo before their incorporation into the PSII complex.

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Photosystem I oligomerization affects lipid composition in Synechocystis sp. PCC 6803.

Project description:In cyanobacteria, increasing growth temperature decreases lipid unsaturation and the ratio of monomer/trimer photosystem I (PSI) complexes. In the present study we applied Fourier-transform infrared (FTIR) spectroscopy and lipidomic analysis to study the effects of PSI monomer/oligomer ratio on the physical properties and lipid composition of thylakoids. To enhance the presence of monomeric PSI, a Synechocystis sp. PCC6803/?psaL mutant strain (PsaL) was used which, unlike both trimeric and monomeric PSI-containing wild type (WT) cells, contain only the monomeric form. The protein-to-lipid ratio remained unchanged in the mutant but, due to an increase in the lipid disorder in its thylakoids, the gel to liquid-crystalline phase transition temperature (Tm) is lower than in the WT. In thylakoid membranes of the mutant, digalactosyldiacylglycerol (DGDG), the most abundant bilayer-forming lipid is accumulated, whereas those in the WT contain more monogalactosyldiacylglycerol (MGDG), the only non-bilayer-forming lipid in cyanobacteria. In PsaL cells, the unsaturation level of sulphoquinovosyldiacylglycerol (SQDG), a regulatory anionic lipid, has increased. It seems that merely a change in the oligomerization level of a membrane protein complex (PSI), and thus the altered protein-lipid interface, can affect the lipid composition and, in addition, the whole dynamics of the membrane. Singular value decomposition (SVD) analysis has shown that in PsaL thylakoidal protein-lipid interactions are less stable than in the WT, and proteins start losing their native secondary structure at much milder lipid packing perturbations. Conclusions drawn from this system should be generally applicable for protein-lipid interactions in biological membranes.

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Project description:Arsenic is a ubiquitous contaminant and a toxic metalloid which presents two main redox states in nature: arsenite [As(III)] and arsenate [As(V)]. Arsenic resistance in Synechocystis sp. strain PCC 6803 is mediated by the arsBHC operon and two additional arsenate reductases encoded by the arsI1 and arsI2 genes. Here we describe the genome-wide responses to the presence of arsenate and arsenite in wild type and mutants in the arsenic resistance system. Both forms of arsenic produced similar responses in the wild type strain, including induction of several stress related genes and repression of energy generation processes. These responses were transient in the wild type strain but maintained in time in an arsB mutant strain, which lacks the arsenite transporter. In contrast, the responses observed in a strain lacking all arsenate reductases were somewhat different and included lower induction of genes involved in metal homeostasis and Fe-S cluster biogenesis, suggesting that these two processes are targeted by arsenite in the wild type strain. Finally, analysis of the arsR mutant strain revealed that ArsR seems to only control 5 genes in the genome. Furthermore, the arsR mutant strain exhibited hypersentivity to nickel, copper and cadmium and this phenotype was suppressed by mutation in arsB but not in arsC gene suggesting that overexpression of arsB is detrimental in the presence of these metals in the media.

| S-EPMC4010505 | biostudies-literature

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