Chromophores of allophycocyanin and R-phycocyanin

Lactic Acid Fermentation of Arthrospira platensis (Spirulina) in a Vegetal Soybean Drink for Developing New Functional Lactose-Free Beverages

The main objective of this study was to evaluate the suitability of Arthrospira platensis F&M-C256 (spirulina) biomass in a vegetal soybean drink or in water, as substrate for lactic acid fermentation by the probiotic bacterium Lactiplantibacillus plantarum ATCC 8014 (LAB8014) and to evaluate the fermented products in terms of bacteria content and organic acids content, biochemical composition, total phenolics, and phycocyanin content, in vitro digestibility, in vitro and in vivo antioxidant activity. After 72 h of fermentation, a bacterial concentration of about 10.5 log CFU mL^–1 in the broths containing the soybean drink + spirulina + LAB8014 (SD + S + LAB8014) or water + spirulina + LAB8014 (W + S + LAB8014) was found. Lactic acid concentration reached similar values (about 1.7 g L^–1) in the two broths, while a different acetic acid concentration between SD + S + LAB8014 and W + S + LAB8014 broths was observed (7.7 and 4.1 g L^–1, respectively). A. platensis biomass was shown to be a suitable substrate for LAB8014 growth. After fermentation, both broths contained a high protein content (>50%). In both broths, total phenolics, in vitro and in vivo antioxidant activity increased after fermentation (+35, +20, and +93% on average, respectively), while phycocyanin content decreased (−40% on average). Digestibility of W + S + LAB8014 broth statistically improved after fermentation. This study highlights the potential of A. platensis F&M-C256 biomass as a substrate for the production of new functional lactose-free beverages.

Isolation, crystallization, crystal structure analysis and refinement of allophycocyanin from the cyanobacterium Spirulina platensis at 2.3 A resolution

The phycobiliprotein allophycocyanin from the cyanobacterium Spirulina platensis has been isolated and crystallized. The crystals belong to space group P6(3)22 with cell constants a = b = 101.9 A, c = 130.6 A, alpha = beta = 90 degrees, gamma = 120 degrees, with one (alpha beta) monomer in the asymmetric unit. The three-dimensional structure of the (alpha beta) monomer was solved by multiple isomorphous replacement. The crystal structure has been refined in a cyclic manner by energy-restrained crystallographic refinement and model building. The conventional crystallographic R-factor of the final model is 19.6% with data from 8.0 to 2.3 A. The molecular structure of the subunits resembles other solved phycobiliprotein structures. In comparison to C-phycocyanin and b-phycoerythrin the major differences arise from deletions and insertions of segments involved in the protein-chromophore interactions. The stereochemistry of the alpha 84 and beta 84 chiral atoms are C(2)-R, C(3)-R and C(31)-R. The configuration (C(4)-Z, C(10)-Z and C(15)-Z) and the conformation (C(5)-anti, C(9)-syn and C(14)-anti) are equal for both chromophores.

Properties of allophycocyanin II and its alpha- and beta-subunits from the thermophilic blue--green alga Mastigocladus laminosus

Purified allophycocyanin II and its subunits have been examined with respect to spectroscopic properties, sedimentation, reconstitution and isoelectric behaviour. In 0.02m-potassium phosphate buffer, pH8.0, and at a concentration of 0.25mg/ml, allophycocyanin II and its alpha- and beta-subunits show visible absorption maxima at 650, 615 and 615nm respectively, whereas the fluorescence emission maxima were determined to be at 662, 640 and 630nm respectively. The absorption difference spectrum (dilution difference) of allophycocyanin II displays maxima at 650 and 590nm with a minimum at 610nm. The c.d. spectrum of allophycocyanin II showed only one positive-ellipticity band at 635nm, and a major negative-ellipticity band at 340nm. Oxidation of allophycocyanin II, low- and high-pH solutions (pH3.0 and 11.0), various ethanol concentrations as well as dialysis against distilled water induce a spectral change leading to phycocyanin-like characteristics. In most cases these shifts are reversible. Allophycocyanin II is thermostable over a period of 60min at temperatures up to 60 degrees C. The isoelectric points of allophycocyanin II and its alpha- and beta-subunits are 4.65, 4.64 and 4.82 respectively. Estimated molecular weights from sedimentation-equilibrium analyses were 102500 for allophycocycanin II, 16000 for the alpha- and 31500 for the beta-subunit. Recombination of alpha- and beta-subunits leads to allophycocyanin II, which is indistinguishable from native allophycocyanin with respect to its spectral form, to its gel-filtration and to its electrophoretic behaviour.

Some properties of allophycocyanin from a thermophilic blue-green alga

Allophycocyanin was purified from the extremely thermophilic blue-green alga Synechococcus lividus. It was shown to be more stable to thermal or urea denaturation than allophycocyanin from a mesophilic organisms. Its amino acid composition and spectroscopic response to pH were investigated. An analysis was made of the relatively low fluorescence polarization of allophycocyanin compared to that of a comparable sized aggregate of the biliprotein, C-phycocyanin. A rather speculative conclusion was reached that suggests that the lower polarization of allophycocyanin may be caused by orientations or positioning of the chromophores that are more favorable for intra-protein energy transfer.

Properties and N-terminal sequence of allophycocyanin from the unicellular rhodophyte Cyanidium caldarium

Allophycocyanin from the unicellular rhodophyte Cyanidium caldarium was purified by (NH4)2SO4 fractionation and ion-exchange chromatography on brushite (calcium phosphate) columns and on DEAE-Sephadex A-25 columns. The specific absorption coefficient (A0.1%1cm) at 650nm of purified allophycocyanin was 6.35 in 0.05M-potassium phosphate buffer, pH7.0. Absorption maxima of allophycocyanin occurred at 650, 618 (shoulder), 350 and 275 nm. Circular-dichroic spectra displayed positive-ellipticity bands at 658 and 630 nm and a major negative-ellipticity band at 340nm. Computer analysis of the circular-dichroic spectrum of allophycocyanin from 207 to 243 nm indicated 42% alpha-helix and 58% beta-form. The estimated molecular weight of purified allophycocyanin on calibrated Sephadex G-200 columns at pH7.0. was 196000. Electrophoretic examination of allophycocyanin on sodium dodecyl sulphate/polyacrylamide gels revealed a single band with apparent mol.wt. 16000. The presence of two polypeptide subunits, with nearly the same molecular weight, was revealed on polyacrylamide gels by using a modified electrophoresis buffer. Spectral analysis of the allophycocyanin subunits resolved by ion-exchange chromatography on Bio-Rex 70 columns indicated that a single phycocyanobilin chromophore was present on each polypeptide chain. Treatment of allophycocyanin with 8M-urea (pH3.0) and subsequent removal of urea by dialysis against water yielded a derivative phycobiliprotein with spectroscopic characteristics similar to those of phycocyanin. The original allophycocyanin spectrum was regenerated after incubation in phosphate buffer, pH7.0. Automated sequences analysis of the N-terminus of allophycocyanin showed that (a) the sequences of the two subunits were different from one another and were different from the subunits of phycocyanin from the same alga, (b) the subunits occurred in a molar ratio of 1:1 and (c) the sequences homology at the N-terminus among alpha- and beta-subunits of allophycocyanin from blue-green and red algae approached 90%.

Characterization and structural properties of the major biliproteins of Anabaena sp

Studies are presented of the biliproteins of Anabaena sp. This filamentous cyanobacterium contains three major biliproteins. Whereas two of these, C-phycocyanin and allophycocyanin, are common to all cyanobacteria, the third, phycoerythrocyanin (gammamax approximately 568 nm) has hitherto not been described and its distribution among cyanobacteria appears to be limited. Anabaena variabilis and Anabaena sp. 6411 allophycocyanin, C-phycocyanin, and phycoerythrocyanin were purified to homogeneity and characterized with respect to molecular weight, isoelectric point, absorption spectrum and amino acid composition. The alpha and beta subunits of each of these proteins were also purified to homogeneity and characterized in the same manner. The tetrapyrrole chromophore content was determined for each of the proteins and subunits. The alpha subunit of phycoerythrocyanin carries a novel phycobiliviolin-like chromophore. This chromophore has not previously been detected in cyanobacterial biliproteins, but has been noted as a prosthetic group of a cryptophytan phycocyanin. Sedimentation equilibrium studies show that at pH 7.0, at protein concentrations of 0.2-0.6 mg/ml, allophycocyanin, C-phycocyanin and phycoerythrocyanin, each exists as a trimeric aggregate, (alphabeta)3, of molecular weight of approximately 105000. Structrual studies of microcrystals of these three biliproteins by electron microscopy and X-ray diffraction reveal a common plan for the construction of higher assembly forms. The major building block appears to be the trimer (alphabeta)3. It is proposed that this is a disc-like structure about 3.0 X 12.0 nm. The individual alpha or beta subunits are roughly spherical, 3 nm in diameter. Allophycocyanin trimers stack to form bundles of rods which form long needles. Both phycocyanin and phycoerythrocyanin form double discs (alphabeta)6 which are visible as ring-shaped structures by electron microscopy. The mode of assembly of the biliprotein structures in the phycobilisome is, as yet, unknown.

A comparison of cryptophytan phycocyanins

The spectroscopically different phycocyanins present in the type strain of Hemiselmis virescens, Millport 64, and in a second strain of this cryptophytan species, Plymouth 157, have been purified and compared. They are similar in native molecular weight and in subunit structure, both containing alpha and beta subunits with molecular weights of approximately 10000 and 19000 respectively. However, they do not have the same chromophore composition. Both subunits of the phycocyanin of Plymouth 157 contain two bilins with absorption maxima at 600 and 660 nm, respectively. Only the beta subunit of Milllport 64 carries these chromophores; its alpha subunit bears another chromophore, with absorption maxima at 368 and 694 nm. The spectroscopic differences between the two native phycocyanins can be entirely accounted for by their differing chromophore compositions. The phycocyanin of Millport 64 is the only biliprotein so far described which contains three chemically different chromophores.

Subunits of phycoerythrin from Fremyella diplosiphon: chemical and immunochemical characterization

The alpha and beta subunits of the phycobiliprotein, phycoerythrin, isolated from the filamentous blue-green alga, Fremyella diplosiphon, have been separated by chromatography on Bio-Rex 70 ion exchange resin. Analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis shows no detectable cross-contamination of these subunit preparations. The molar extinction coefficients at 552 nm of the alpha and beta subunits in 8 M urea are 25,549 and 48,456, respectively. The amino acid compositions of the subunits are very similar. Molecular weights of the alpha and beta subunits are 19,500 and 21,700, respectively, based on the amino acid composition analyses. Antisera prepared against the alpha subunit reacts with the beta subunit, and vice versa. Tryptic peptide maps reveal that the subunits share share at least eight common tryptic peptides. These results indicate that the phycoerythrin subunits are chemically very similar.

Physiology and cytological chemistry blue-green algae

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Formation of carbon monoxide and bile pigment in red and blue-green algae

Five blue-green and one red algal species produced carbon monoxide during photosynthetic growth. The blue-green algae synthesized CO and phycocyanobilin in equimolar quantities at identical rates. The red alga, Porphyridium cruentum, incorporated Delta-aminolevulinic acid-5-(14)C into phycoerythrobilin and CO. The ratio of the specific radioactivity of phycoerythrobilin to that of CO, and the kinetics and stoichiometry of phycocyanobilin and CO formation suggest that linear tetrapyrroles in plants are derived by the porphyrin pathway via the intermediate formation of heme. The similarity between bile pigment production in algae and in mammalian systems is discussed.

Comparative immunology of algal biliproteins

The three spectroscopically distinct classes of phycobiliproteins characteristic of the Cyanophyta and Rhodophyta-phycocyanins, allophycocyanins, and phycoerythrins-share no common antigenic determinants detectable by the Ouchterlony double diffusion technique. Each class of phycobiliprotein, from both Cyanophyta and Rhodophyta, possesses a strong determinant common to all members of that class. With respect to an antiserum directed against a specific cyanophytan biliprotein, all heterologous biliproteins of the same class are immunologically identical, as shown by the fact that absorption with a given heterologous antigen simultaneously eliminates crossreactions with other heterologous antigens. A cryptophytan phycoerythrin was found to be immunologically unrelated to any of the cyanophytan or rhodophytan biliproteins examined.

Free and membrane-bound ribosomes of the cotyledons of Vicia faba (L.) : II. Seed germination

During the first few days of germination, the RNA content of the cotyledons remained approximately constant, but the quantity of membrane-bound ribosomes increased. Experiments with orthophosphate-(32)P indicated that these ribosomes were synthesised de novo, and did not originate by the attachment to membranes of pre-existing free ribosomes. This conclusion was discussed in relation to the suggestion that free and membrane-bound ribosomes synthesise different groups of proteins.