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PubMedDate not supplied

Comparative immunological detection of lipids and carotenoids on peptides of photosystem I from higher plants and cyanobacteria.

Photosystem I preparations were obtained from wild-type tobacco Nicotiana tabacum var. JWB, three chlorophyll-deficient tobacco mutants: Su/su, Su/su var. Aurea and yellow-green leaf patches of the variegated mutant NC 95, Spinacia oleracea and furthermore from the mesophilic cyanobacterium Synechococcus PCC 7942 and the thermophilic cyanobacterium Synechococcus sp.. Peptides from these preparations were analyzed by SDS polyacrylamide gel electrophoresis and transferred for detection of bound lipids and carotenoids according to the Western blot procedure to nitrocellulose membranes. The PS I preparations from the Nicotiana tabacum species and spinach consist of the core complex and the LHCP I complex, the latter containing, however, traces of the LHCP II polypeptides. The core complex consists of the two core peptides with the apparent molecular mass of 66 kDa each and peptides with molecular masses of 22, 20, 19, 17, 16, 10 and 9 kDa. The LHCP I complex contains 4 subunits with molecular masses of 28, 26, 25 and 24 kDa. The PS I preparations of the two mutants Su/su and Su/su var. Aurea contain as impurities traces of the core peptides (D1/D2) and the two chlorophyll-binding peptides (CP43/CP47) of photosystem II. The PS I preparation from the mesophilic and thermophilic cyanobacterium consists of the two core peptides with the apparent molecular mass of 66 kDa and peptides with molecular masses of 16, 14 and 10 kDa. The peptides of the PS I preparations were characterized by specific PS I, CP I and LHCP I antisera. The antiserum to the PS I complex reacts in the Western blot with the homologous peptides of PS I from higher plants, but only with the CP I complex from the two cyanobacteria. In comparative studies with PS II from higher plants the PS I antiserum reacts with the LHCP II complex as expected. The antiserum to the CP I complex reacts only with the 66 kDa peptides of PS I from all objects. There is no cross reaction with the 66 kDa peptides (heterodimer of the D1/D2 peptides) of PS II. The antiserum to the LHCP I complex reacts only with the four LHCP I peptides of PS I from higher plants and as expected with the LHCP II of PS II: Because cyanobacteria do not have LHCP complexes, there is no reaction with the LHCP I antiserum. By means of polyclonal monospecific antisera to lipids it was shown by Western blot procedure that only two lipid species are bound to PS I peptides. The galactolipid monogalactosyldiglyceride is bound to the CP I complex of the Nicotiana tabacum species, spinach and the two cyanobacteria as well as to the LHCP I complex of the higher plants. The phospholipid phosphatidylglycerol is only associated with the CP I complex of the analyzed higher plants and cyanobacteria. With polyclonal monospecific antisera to carotenoids it was demonstrated that beta-carotene, lutein, neoxanthin and zeaxanthin are associated with the CP I complex of the higher plants and the cyanobacteria analyzed. Violaxanthin is also bound to the CP I complex of the two cyanobacteria, whereas it is bound together with neoxanthin to the LHCP I complex of the higher plants.

Animals↗
PubMedDate not supplied

Dependence of the flash-induced oxygen evolution pattern on the chemically and far red light-modulated redox condition in cyanobacterial photosynthetic electron transport.

Flash-induced photosynthetic oxygen evolution was measured in cells and thylakoid preparations from the coccoid cyanobacteria Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7942 and from the filamentous cyanobacterium Oscillatoria chalybea. The resulting characteristic flash patterns from these cyanobacteria can be chemically altered by addition of exogenously added substances like CCCP, DCPiP and inorganic salts. Potassium chloride, manganese sulfate and calcium chloride affected the sequences by specific increases in the flash yield and/or effects on the transition parameters. Chloride appeared to exert the strongest stimulatory effect on the oxygen yield. In comparison to chloride, both manganese and calcium did not significantly stimulate the flash amplitudes as such, but improved the functioning of the oxygen evolving complex by decreasing the miss parameter alpha. Particular effects were observed with respect to the time constants of the relaxation kinetics of the first two flash signals Y1/Y2 of the cyanobacterial patterns. In the presence of the investigated chemicals the amplitudes of the first two flash signals (Y2 in particular) were increased and the relaxation kinetics were enhanced so that the time constant became about identical to the conditions of steady state oxygen flash amplitudes. The results provide further evidence against a possible participation of either PS I or respiratory processes to Y1/Y2 of cyanobacterial flash patterns. Dramatic effects were observed when protoplasts from Oscillatoria chalybea or cells from Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7942 were exposed to weak far red background illumination. Under these conditions, Y2 (and to a smaller extent Y1) of otherwise unchanged flash sequences were specifically modified. Y2 was substantially increased and again the relaxation kinetics were accelerated making the signal indistinguishable from a Y(SS) signal. From the mathematical fit of the sequences we conclude that S2 contributes to 10-20% of the S-state distribution (in comparison to 0% in the control). Thus, far red background illumination might represent a valuable means for photosynthetic investigations where high amounts of S2 are required like e. g. EPR measurements. In such experiments the corresponding EPR signals appeared substantially enhanced following far red preillumination (Ahrling and Bader, unpublished observations). Our results clearly show that the 'controversial results' from parts of the literature suggesting the participation of different mechanisms (net oxygen evolution, inhibited uptake processes etc.) are not required to explain the flash-induced oxygen evolution in cyanobacteria: the seemingly 'incompatible' conditions and conformations can be perfectly interconverted by different modulation techniques (chemicals, far red) of the respective redox condition within the water oxidation complex of photosynthesis.

2,4-Dinitrophenol↗
PubMed2003

Sensitivity of cyanobacterial antenna, reaction center and CO2 assimilation transcripts and proteins to moderate UVB: light acclimation potentiates resistance to UVB.

We tested the hypothesis that cyanobacterial cells have sufficient acclimation potential to tolerate UVB when it is applied in a natural quantum ratio to growth photosynthetically active radiation (PAR). We grew Synechococcus under 50 (Low) or 300 (High) micromol PAR m(-2) x s(-1) and then exposed the cells to 0.125 (Low) or 0.75 (High) micromol UVB m(-2) x s(-1). The PAR:UVB quantum ratios were near natural for both the Low-PAR:Low-UVB and the High-PAR:High-UVB treatments, but UVB was in excess of typical aquatic PAR:UVB for Low-PAR:High-UVB treatments. The cellular light history determined the UVB responses of Synechococcus. High-PAR cells initially had fewer cpc transcripts encoding phycocyanin, lower phycocyanin content, and more psbAII/AIII transcripts encoding the D1:2 photosystem II (PSII) protein isoform. Higher PAR potentiated them to tolerate an appropriate UVB level without short-term inhibition of PSII or growth. Low-PAR cells rapidly altered psbAII/AIII and cpc gene expression and tolerated appropriate Low UVB. Low-PAR:High-UVB cells, in contrast, suffered short-term inhibition of PSII and growth. In all treatments UVB induced transient loss of cpc transcripts, possibly to free resources for psbAII/AIII expression, which is important for UVB resistance. The drop in cpc transcripts was not part of a general shock response because rbcL transcript pools were stable upon UVB exposure.

Adaptation, Physiological↗
PubMed2005

Comparison of Cd, Cu, and Zn toxic effects on four marine phytoplankton by pulse-amplitude-modulated fluorometry.

The toxic effects of Cd, Cu, and Zn on four different marine phytoplankton, Dunaliella tertiolecta, Prorocentrum minimum, Synechococcus sp., and Thalassiosira weissflogii, were examined by comparing the cell-specific growth rate, pulse-amplitude-modulated (PAM) parameters (maximum photosystem II quantum yield phiM and operational quantum yield phi'M, chlorophyll a content, and cellular metal concentration, over a 96-h period. The calculated no-observed-effect concentration (NOEC) based on both cell-specific growth rate and two PAM parameters (phiM and phi'M) were mostly identical. Thus, these PAM parameters and cell-specific growth rate were comparable in their sensitivities as the biomarkers for trace metal toxicity to marine phytoplankton. The cyanobacteria Synechococcus sp. was the most sensitive species among the four algal species tested because of its higher cell surface to volume ratio. The toxicity of the three tested metals followed the order of Cd > Cu > Zn based on the cellular metal concentration of the four algae at the NOEC. The cellular metal bioaccumulation followed the same Freundlich isotherm for each metal regardless of the algal species, indicating that the metal accumulation was a nonmetabolic process under high ambient metal concentrations and that the cell surface metal binding was comparable among the different species. For all the algae examined in our study, the bioaccumulation potentials of Cu and Zn were similar to each other, while the Cd bioaccumulation was much lower under environmentally realistic metal concentration.

Biomarkers↗
PubMed2000

[Cloning and expression of the detoxifying gene in cyanobacteria].

Plasmid pRL-B1 was constructed from detoxifying gene(called B1) of pesticide resistant Culex and from plasmid pRL-439 containing the strong promoter PpsbA. E. coli-cyanobacteria shuttle expression plasmid pDC-B1 was constructed from shuttle vector pDC-8 and from recombinant plasmid pRL-B1, then it was transferred into Synechococcus sp. PCC7942 by triparental conjugative transfer. The existence of B1 was detected by Southern analysis, and the expression of B1 was confirmed by enzyme activity analysis of detoxification of transgenic cyanobacteria. Experimental results indicated that the transgenic cyanobacteria could degrade beta-naphthyl acetate(beta-NA), a specific substrate of esterase. The enzyme activity of transgenic strain was higher than that of the wild type. It may be the first report on transformation of detoxify gene of pesticide resistant culex into Synechococcus strain.

Animals↗
PubMedDate not supplied

[Use of cyanobacteria for indication of toxic action of stachybotrys toxins].

Screening of cyanobacteria cultures for their sensitivity to the action of complex preparations of toxins from 18 strains of Stachybotrys chartarum has been carried out with the purpose to search for new test-organisms to create a reliable system of biotesting of stachibotryotoxines. In contrast to other cultures of unicell (Anacystis nidulans) and filamentous (Anabaena sp., Anabaena variabilis, Nostoc linckia, Plectonema boryanum) cyanobacteria used in the experiment, only one culture of unicell cyanobacterium Synechococcus cedrorum proved to be highly sensitive to the action of preparations of the whole group of studied mycotoxins. Their activity with respect to this culture varied within wide limits (lysis zone diameter is 11-30 mm) and for the most of strains it coincided with or exceeded this index determined with the use of other biotests. Owing to the use of Synechococcus cedrorum as test culture the authors have proved for the first time the toxicity of three strains of Stachybotrys chartarum (K15822, 14722, 14186). Basing on the data obtained the authors have determined the culture of the unicell cyanobacterium, according to the sign of high sensitivity to all the studied stachibotryotoxin preparations of solid and liquid nutrient media, as a new test-organism for detection of this group of toxins and it may be recommended for practical use. Optimal conditions for growing test-culture and biotesting of toxins have been defined.

Biological Assay↗
PubMed2003

[Toxic effects of hexavalent chromium on the growth of blue-green microalgae].

A standard method of algal bioassay for determining the toxicity of toxic chemicals was applied to the interaction between Cr(VI) and six blue-green microalgae. The 96h-EC50 of hexavalent chromium on the growth of Chlorella pyrenoidosa, Synechococcus, Spirulina maxima, Spirulina platensis, Selenastrum capriornutum and Scenedesmus quadricauda were 4.96, 6.50, 11.16, 11.74, 12.43 and 20.89 mg/L, respectively. The tolerance of the six blue-green microalgae to Cr(VI) was in the order of Scenedesmus quadricauda > Selenastrum capriornutum > Spirulina platensis > Spirulina maxima > Synechococcus > Chlorella pyrenoidosa. The sensitivity of these species to Cr(VI) might relate to the cell size, the structure of cell wall, as well as the redox reaction caused by the exudate or enzyme. X-ray absorption near edge structure(XANES) was used to study the accumulation and transformation of Cr(VI) in Chlorella pyrenoidosa.

Carcinogens, Environmental↗
PubMed2004

[Cloning and analysis of cDNA encoding key enzyme gene (dxr) of the non-MVA pathway in Taxus chinensis cells].

Two distinct routes (classical mevalonate pathway and a novel mevalonate-independent pathway) are utilized by plants for the biosynthesis of isopentenyl diphosphate, the universal precursor of isoprenoids (Fig. 1). Present researches indicated that taxol was synthesized mainly via non-mevalonate pathway, but not genetic evidence was showed. The second step in non-mevalonate pathway involves an intramolecular rearrangement and subsequent reduction of deoxyxylulose phosphate to yield 2-C-methyl-D-erythritol-4-phosphate, and 1-Deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) with responsibility for this reaction was considered as a key enzyme. As a tool for the isolation of genes in terpenoid biosynthesis in plants, total RNA was prepared from Taxus chinensis suspension cells, a cell type highly specialized for diterpene (taxol). A reverse transcription-PCR strategy based on the design of degenerated oligonucleotides was developed for isolating the gene encoding a gymnosperm homolog of this enzyme from Taxus chinensis. Through sequence analysis by Blast P online, the resulting cDNA showed highly homologous to 1-deoxy-D-xylulose 5-phosphate reductoisomerases, with 95% identification compared with Arabidopsis thaliana (Q9XFS9), 94% with Mentha x piperita (Q9XESO), 80% with Synechococcus elongatus (Q8DK30), 78% with Synechocystis sp. PCC 6803 (Q55663) and Nostoc sp. PCC 7120 (Q8YP49), and 73% with Synechococcus leopoliensis (Q9RKT1). Deduced amino acid sequences were also analyzed by PROSITE, ClustalX (1.81) and Phylio (3.6 alpha), and data present evidence for the existence of this deoxyxyluose phosphate reductoisomerase in Taxus chinensis. This is the first report of the dxr gene cloned from gymnosperm.

Aldose-Ketose Isomerases↗
PubMed1988

Exclusive A-ring linkage for singly attached phycocyanobilins and phycoerythrobilins in phycobiliproteins. Absence of singly D-ring-linked bilins.

Previous spectroscopic studies on the phycocyanobilin-containing peptide beta-2T from Synechococcus sp. 6301 C-phycocyanin and the phycoerythrobilin-containing peptide beta-2TP from Porphyridium cruentum B-phycoerythrin indicated a different single thioether mode of attachment, postulated to be through the D-ring of the tetrapyrrole, in contrast to the A-ring linkage established for the other singly linked bilins in these proteins (Bishop, J.E., Lagarias, J.C., Nagy, J. O., Schoenleber, R.W., Rapoport, H., Klotz, A.V., and Glazer, A.N. (1986) J. Biol. Chem. 261, 6790-6796; Klotz, A.V., Glazer, A.N., Bishop, J.E., Nagy, J.O., and Rapoport, H. (1986) J. Biol. Chem. 261, 6797-6805). The crystal structure of Agmenellum quadruplicatum C-phycocyanin at 2.5-A resolution (Schirmer, T., Bode, W., and Huber, R. (1987) J. Mol. Biol., 196, 677-695) supports an A-ring linkage for all three phycocyanobilins. Consequently we have re-evaluated our proposed structural assignments by further 1H NMR studies. Two-dimensional homonuclear correlated and nuclear Overhauser enhancement spectroscopic data presented here show that all three bilins in Synechococcus 6301 C-phycocyanin are attached solely through the A-ring, complementary to the crystallographic data. The evidence from the NMR data for all bilin peptides examined includes the dipoledipole interactions of the 5-H with the 3-H, 3'-H, and a pyrrole methyl group (7-CH3); the corresponding interactions would not be possible in a D-ring-linked bilin. The 5-H also consistently exhibits allylic J-coupling to the 3-H, supporting A-ring linkage assignment. These data are inconsistent with the alternative D-ring linkage assignment since this would involve J-coupling through five bonds. Examination of the phycoerythrobilin beta-2 position in B-phycoerythrin also reveals an A-ring type of attachment by similar criteria. We conclude that all singly linked bilins are attached through the A-ring.

Chemical Phenomena↗
PubMed1993

Rod structure of a phycoerythrin II-containing phycobilisome. II. Complete sequence and bilin attachment site of a phycoerythrin gamma subunit.

The major phycoerythrins of marine unicellular cyanobacteria Synechococcus spp. and those of red algae are isolated as stable complexes with the composition (alpha beta)6 gamma. The gamma subunits carry bilins and in this respect are unique among phycobilisome rod linker polypeptides. There has been no complete amino acid sequence data on any gamma subunit. Synechococcus sp. WH8020 phycoerythrin II (PE II) gamma subunit was isolated from purified PE II hexamers. Partial amino acid sequence determination showed that the gamma subunit was encoded by the mpeC gene, an open reading frame 275 base pairs 3' of mpeA and mpeB, which encode the alpha and beta subunits of PE II, respectively (Wilbanks, S. M., and Glazer, A. N. (1993) J. Biol. Chem. 268, 1226-1235). A single phycourobilin is attached through a thioether bond to gamma-Cys-49. Derivatization with 4-vinylpyridine showed that the only other cysteinyl residue, gamma-Cys-64, is unsubstituted. MpeC encodes a polypeptide of 293 residues with a predicted molecular weight of 32,100 and a pI of 8.9. These properties are like those of non-bilin-bearing linker polypeptides associated with C-phycoerythrin and hence the gamma subunit is designated gamma (LR32). Alignment of the sequence of the PE II-gamma with those of the latter polypeptides shows that PE II-gamma has a 49-residue extension at the N terminus, that encompasses the phycourobilin attachment site, and is shorter by a similar number of residues at the C terminus. These differences in linker polypeptide structure offer a possible explanation for the observed much higher stability of PE II hexamers relative to those of C-phycoerythrins.

Amino Acid Sequence↗
PubMed1993

Construction of Zn2+/Cd2+ hypersensitive cyanobacterial mutants lacking a functional metallothionein locus.

Eukaryotic metallothioneins (MTs) have been extensively studied, but the precise functions of most of these molecules are not yet fully understood. Prokaryotes are often more tractable for the analysis of gene function and we report here the generation of mutants of Synechococcus PCC 7942 (strain R2-PIM8) deficient in the MT locus, smt. Viability of these mutants, designated R2-PIM8 (smt), reveals that prokaryotic MT performs no "vital" role (such as donation of metals to metallo-proteins) in Synechococcus. R2-PIM8 (smt) has reduced (approximately 5-fold) tolerance to elevated Zn2+, with detectable hypersensitivity to Cd2+. Restoration of Zn2+ tolerance was used as a selectable marker to isolate recombinants derived from R2-PIM8(smt) after reintroduction of a linear DNA fragment containing an uninterrupted smt locus. These smt-complemented cells also exhibited restored Cd2+ tolerance. Hypersensitivity to Cu2+ was not detected in R2-PIM8(smt) indicating independence of Cu2+ resistance from smt mediated metal (Zn2+/Cd2+) tolerance.

Cadmium↗
PubMed1998

Construction of a marine cyanobacterial strain with increased heavy metal ion tolerance by introducing exogenic metallothionein gene.

A marine cyanobacterial strain with enhanced heavy metal ion tolerance was constructed by introducing an exogenous cyanobacterial metallothionein gene, smtA, from a freshwater unicellular cyanobacterium, Synechococcus sp. PCC 7942. An expression vector harboring the c-phycocyanin (cpc) promoter and cpc N-terminal region was constructed and smtA was inserted into its multiple cloning site. The marine cyanobacterium, Synechococcus sp. NKBG 15041c, was highly sensitive to the heavy metal ions present in the medium. However, the recombinant marine cyanobacteria harboring the expression vector with smtA could grow even in the presence of 4 µM of CdCl2, at which concentration the wild-type strain did not grow.

Journal Article↗
PubMed2006

Model-supported optimization of phototrophic growth in a stirred-tank photobioreactor.

A fuzzy-logic light attenuation model was developed and validated for a stirred-tank photobioreactor. Based on this model, local light intensities were used to calculate local specific growth rates of the cyanobacteria Synechococcus PCC 7942. The light regime for maximization of biomass space-time yield in a batch process was estimated using a genetic algorithm taking into account the integral average of the individual growth rates.

Algorithms↗
PubMed2006

Toxic Microcystis is widespread in Lake Erie: PCR detection of toxin genes and molecular characterization of associated cyanobacterial communities.

During the past decade, algae blooms, which include the toxic cyanobacterium Microcystis, have reoccurred in the Laurentian Great Lakes, most commonly in the western basin of Lake Erie. Whereas the western basin is the most impacted by toxic Microcystis in Lake Erie, there has historically been little effort focused on identifying the spatial distribution of Microcystis throughout this lake. To address this lack of knowledge, we have employed a polymerase-chain-reaction-based detection of genes required for synthesis of the toxin microcystin (mcyD and mcyB), as well as 16S rDNA fragments specific to either all Microcystis or all cyanobacteria. Using a multiplex approach, we tested 21 samples from 13 field stations and found that toxigenic Microcystis were present in the western and eastern basins in the summers of 1999, 2000, and 2002 and the central basin in 1999 and 2002. This is the most extensive distribution of Microcystis reported in Lake Erie. Clone libraries (16S rDNA) of these cyanobacterial communities were generated from 7 of the 13 field stations (representing all three basins) to partially characterize this microbial community. These libraries were shown to be dominated by sequences assigned to the Synechococcus and Cyanobium phylogenetic cluster, indicating the importance of picoplankton in this large lake system.

Bacterial Toxins↗
PubMed2005

Red chlorophylls in the exciton model of photosystem I.

Structural arrangement of pigment molecules of Photosystem I of photosynthetic cyanobacterium Synechococcus elongatus is used for theoretical modeling of the excitation energy spectrum. It is demonstrated that a straightforward application of the exciton theory with the assumption of the same molecular transition energy does not describe the red side of the absorption spectrum. Since the inhomogeneity in the molecular transition energies caused by a dispersive interaction with the molecular surrounding cannot be identified directly from the structural model, the evolutionary search procedure is used for fitting the low temperature absorption and circular dichroism spectra. As a result, one dimer, three trimers and one tetramer of chlorophyll molecules responsible for the red side of the absorption spectrum with their assignment to the spectroscopically established three bands at 708, 714 and 719 nm are determined. All of them are found to be situated not in the very close vicinity of the reaction center but are encircling it almost at the same distance. In order to explain the unusual broadening on the red side of the spectrum the exciton state mixing with the charge transfer (CT) states is considered. It is shown that two effects can be distinguished as caused by mixing of those states: (i) the oscillator strength borrowing by the CT state from the exciton transition and (ii) the borrowing of the high density of the CT state by the exciton state. The intermolecular vibrations between two counter-charged molecules determine the high density in the CT state. From the broad red absorption wing it is concluded that the CT state should be the lowest state in the complexes under consideration. Such mixing effect enables resolving the diversity in the molecular transition energies as determined by different theoretical approaches.

Chlorophyll↗
PubMed2005

Post-transcriptional control of the cyanobacterial hspA heat-shock induction.

The hspA gene encodes a small heat-shock protein in the thermophilic cyanobacterium Synechococcus vulcanus. To gain insight into the post-transcriptional regulation, hspA was expressed in Escherichia coli. HspA was induced upon a temperature upshift from 30 to 42 degrees C, although the hspA transcription in E. coli occurred constitutively at both 30 and 42 degrees C. Neither replacement of the native hspA promoter with the lacZ promoter nor the addition of rifampin abolished the heat induction. Thus, the primary form of regulation of the heat induction is at the post-transcriptional level. Analyses of expression of a series of the transcriptional and translational hspA-lacZ fusions confirmed the constitutive transcription, and demonstrated that the heat induction occurred only in the translational fusions. They further indicated the presence of regulatory elements involved in the translational regulation. An element in the 5'-untranslated region of the hspA mRNA suppressed the translation, while that in the hspA coding region was required for the de-repression of the translation and for thermal regulation.

Bacterial Proteins↗
PubMed2006

Removal of triazine herbicides from freshwater systems using photosynthetic microorganisms.

The uptake of the triazine herbicides, atrazine and terbutryn, was determined for two freshwater photosynthetic microorganisms, the green microalga Chlorella vulgaris and the cyanobacterium Synechococcus elongatus. An extremely rapid uptake of both pesticides was recorded, although uptake rate was lower for the cyanobacterium, mainly for atrazine. Other parameters related to the herbicide bioconcentration capacity of these microorganisms were also studied. Growth rate, biomass, and cell viability in cultures containing herbicide were clearly affected by herbicide uptake. Herbicide toxicity and microalgae sensitivity were used to determine the effectiveness of the bioconcentration process and the stability of herbicide removal. C. vulgaris showed higher bioconcentration capability for these two triazine herbicides than S. elongatus, especially with regard to terbutryn. This study supports the usefulness of such microorganisms, as a bioremediation technique in freshwater systems polluted with triazine herbicides.

Atrazine↗
PubMed2006

Interaction of a small heat shock protein with light-harvesting cyanobacterial phycocyanins under stress conditions.

Phycobiliproteins such as phycocyanins are the most abundant proteins found in cyanobacteria which are assembled to form the phycobilisome. Here, we showed that a small heat shock protein, HspA, interacts directly with phycocyanins from the cyanobacterium Synechococcus sp. strain PCC 7942 in vitro and suppresses inactivation of their light-harvesting functions due to heat denaturation in the presence of hydrogen peroxide. Under the denaturing conditions, phycobilisomes were de-assembled to lighter complexes and then aggregated. HspA associated with phycocyanins in the dissociated complexes, and suppressed the aggregation. The specific interaction between a small heat shock protein and phycocyanins was further supported by the fact that HspA and alpha-crystallin protected isolated phycocyanins from denaturation, while HtpG and lysozyme did not. The maximum protection was observed at a molar ratio of four HspA monomer per one phycocyanin (alpha beta) monomer.

Bacterial Proteins↗