B-Phycoerythrin from Rhodella violacea: characterization of two isoproteins.

Two isoproteins of the "native" B-phycoerythrin of the red alga, Rhodella violacea, were purified from crude extracts by preparative polyacrylamide gel electrophoresis and subsequently characterized. The slower moving pigment in gel electrophoresis was designated B-PE I, the faster as B-PE II. Both were found to occur in about equal amounts. B-PE I has a molecular weight of about 280000 and an IEP at 4.39, B-PE II a molecular weight of nearly 265000 and an IEP at 4.23. B-PE I and II are characterized by absorption maxima at 568 and 542 nm and a shoulder at 500 nm in the visible part of the absorption spectra. Their absorption coefficients at 542 nm differ with values of 5.54 and 5.63, respectively. The fluorescence emission spectra show a single maximum at 575 for B-PE I and at 578 nm for B-PE II. Both spectra have a shoulder at 630 nm. The fluorescence yield of B-PE II is lower by 25%. In calibrated SDS gel electrophoresis of the purified pigments B-PE I and II show two subunits of molecular weights of 18900 and 29200 and 18500 and 29900, respectively. Quantitative amino acid analyses indicated, that the isoproteins are very similar. B-PE II, however, has a significantly higher content of acidic amino acids and a lower percentage of basic residues, which is in keeping with its lower isoelectric point. Functional aspects of the occurrence of two isoproteins of B-phycoerythrin are discussed.     

The effect of ionic stress on photosynthesis in Dunaliella tertiolecta

A comparison of the effects of ionic stress and an uncoupler on long-term fluorescence transients (the Kautsky effect) in the green alga Dunaliella tertiolecta indicated that the large quenching induced by ionic stress was caused by a pH gradient across the thylakoid membrane. This possiblity was given support by the increase in the slow phase of 3-(3,4-dichlorophenyl)-1,1-dimethylurea-induced fluorescence relaxation in algae subjected to ionic stress. Low-temperature fluorescence emission spectra indicated that salt stress enhanced photosystem-I emission in the dark, and a comparison of simultaneous emissions at 695 and 720 nm at room temperature indicated a further increase in photosystem-I emission during the fluorescence transients. Taken together with the decrease in the fast phase of 3-(3,4-dichlorophenyl)-1,1-dimethylurea-induced fluorescence relaxation in stressed algae, our results indicate that ionic stress stimulates cyclic electron flow, and that non-cyclic flow is inhibited. The effect of sucrose-induced osmotic stress was similar to, but less marked than, the effects of NaCl and KCl; the effect of decreasing the external salinity was small.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - FCCP carbonylcyanide p-trifluoromethoxyphenylhydrazone - PSI, II photosystem I, II     

Cryptopolyploidy inBunias (Brassicaceae) revisited — A flow-cytometric and densitometric study

The concern of the present analysis is the hypothetical cryptopolyploidy, a concept basically of historical interest only, but discussed again by Battaglia (1996) in a recent treatment of the term and its historical background. Melinossi (1935), while reanalyzing erratic observations on the crucifersBunias erucago andB. orientalis by Jaretzky (1928a), found 2n = 14 in both species but twice the chromosome volume inB. erucago compared withB. orientalis. Melinossi considered cryptopolyploidy inB. erucago, i.e., she discussed pairwise fused chromosomes on a tetraploid basis or endoreduplicated (and thus binemic) chromosomes in this species. Cryptopolyploidy has also been claimed by Pannocchia-Laj (1938) inVinca difformis (Vincaceae). Battaglia (1996) criticized the term cryptopolyploidy because, in his opinion, the genuinely polyploid status of these plants is not hidden (crypto) but phenotypically (from herbarium specimens) recognizable. He coins the term phenopolyploidy, i.e., phenotypic polyploidy disagreeing with the karyotype numerically evalated. We measured genome size ofB. orientalis andB. erucago (both 2n = 14) by Feulgen densitometry and propidium iodide flow cytometry. Surprisingly,B. erucago (the annual species with 2.13 pg, 1 C) turned out to have only 0.81-fold the DNA amount ofB. orientalis (the perennial species with 2.64 pg, 1 C). Therefore, any kind of genetically polyploid status inB. erucago is out of the question. Only speculative significance can be ascribed to the terms cryptopolyploidy and phenopolyploidy.     

Role of the recF gene of Escherichia coli K-12 in lambda recombination

Summary When Escherichia coli K12() lysogens are infected with heteroimmune phage, which are unable to replicate, general recombination between phage and prophage depends on the bacterial recF gene. It has been shown that in E. coli K12 postconjugational recombination, the RecF pathway only works with full efficiency if exonuclease I is absent (Clark 1973). However, results presented in this paper indicate that under conditions in which replication is blocked, the recombination pathway dependant on the recF gene is fully active in producing viral recombinants even, if the phage is Red⁺, in the presence of exonuclease I. In contrast, removal of exonuclease and protein requires elimination of exonuclease I for an efficient RecF pathway. It is concluded that the Red system cooperates with the RecF pathway and that this cooperation involves overcoming the inhibitory effects of exonuclease I. In the absence of exonuclease, protein stimulates recF-dependent recombination but does not suffice to prevent the negative effect of exonuclease I. In the presence of protein, full efficiency of the RecF pathway can be obtained either via cooperation with exonuclease I or, if the viral exonuclease is defective, via inactivation of exonuclease I. Since activity of exonuclease appears necessary to overcome the inhibitory effects of exonuclease I, it is proposed here that exonuclease diverts material from the RecF pathway in a shunt reaction which allows completion of recF-initiated recombinational intermediates via a mechanism insensitive to exonuclease I.When replication is allowed, the Rec system produces viral recombinants mainly via a recF-independent mechanism. However, a major contribution of the RecF pathway to recombination is observed after removal of the Red system and exonuclease I.Obra social de la Caja de Ahorros de Valencia (Director: S. Grisolía)     

Acclimation of barley to changes in light intensity: photosynthetic electron transport activity and components

Barley seedlings (Hordeum vulgare L. Boone) were grown at 20°C with 16 h/8 h light/dark cycle of either high (H) intensity (500 mole m^-2 s^-1) or low (L) intensity (55 mole m^-2 s^-1) white light. Plants were transferred from high to low (H L) and low to high (L H) light intensity at various times from 4 to 8 d after leaf emergence from the soil. Primary leaves were harvested at the beginning of the photoperiod. Thylakoid membranes were isolated from 3 cm apical segments and assayed for photosynthetic electron transport, Photosystem II (PS II) atrazine-binding sites (Q_B), cytochrome f(Cytf) and the P-700 reaction center of Photosystem I (PS I). Whole chain, PS I and PS II electron transport activities were higher in H than in L controls. Q_B and Cytf were elevated in H plants compared with L plants. The acclimation of H L plants to low light occurred slowly over a period of 7 days and resulted in decreased whole chain and PS II electron transport with variable effects on PS I activity. The decrease in electron transport of H L plants was associated with a decrease in both Q_B and Cytf. In L H plants, acclimation to high light occurred slowly over a period of 7 days with increased whole chain, PS I and PS II activities. The increase in L H electron transport was associated with increased levels of Q_B and Cytf. In contrast to the light intensity effects on Q_B levels, the P-700 content was similar in both control and transferred plants. Therefore, PS II/PS I ratios were dependent on light environment.Abbreviations Asc ascorbate - BQ 2,5-dimethyl-p-benzoquinone - DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - DCIP 2,6-dichlorophenolindophenol - H control plants grown under high light intensity - H L plants transferred from high to low light intensity - L low control plants grown under low light intensity - L H plants transferred from low to high light intensity - MV methyl viologen - P-700 photoreaction center of Photosystem I - Q_B atrazine binding site - TMPD N,N,N,N-tetramethyl-p-phenylenediamine Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, NC. Paper No. 11990 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643, USA.     

Isozyme variation and correspondence with unusual infrared reflectance patterns inPhragmites australis (Poaceae)

Isozyme variation was investigated in populations ofPhragmites australis (Poaceae) which have recently invaded and taken over marsh habitat of the Mississippi River delta. Infrared aerial photographs in the Garden Island Bay subdelta of the extensiveP. australis populations reveal distinct, clone-like circular patches within a predominant background. Preliminary evidence indicates that the infrared color differences represent distinct morphological types. However, there are no obvious environmental factors that could account for the peculiar patterns.P. australis collections were taken from five separate and distinct patches and adjacent background. Only two electrophoretic phenotypes were found: one from patches and one from the background. In comparing the two, 20% of the 40 loci scored are fixed for alternate alleles. These results indicate a clear correspondence of infrared reflectance with electrophoretic phenotype. In addition, the genetic uniformity as evidenced by the discovery of only two electrophoretic phenotypes supports the contention that the recent spread ofP. australis throughout the Mississippi River delta has been primarily, if not exclusively, a result of vegetative propagation.     

Carotenoid pigments in a red strain of Rhizobium from Lotononis bainesii Baker

The carotenoid pigments of a Rhizobium strain isolated from Lotononis bainesii were found to be diglucosyl-4,4-diapocarotene-4,4-dioate and glucosyl-4,4-diapocarotene-4-oate-4-oic acid.5th publication in the series Carotenoids of Rhizobia [4th publication: Helv. chim. Acta 62: 2551–2557 (1979)]     

Growth temperature acclimation byAmoeba proteus: Effects on cytoplasmic organelle morphology

Summary The effects on subcellular morphology of maintaining amoebae at temperatures other than 20 C (the routine culture temperature) were assessed. Estimations of cycling potential at each temperature confirmed that acclimation had affected gross cell functioning. Generation times ranged from no division at 6 C, to an optimal minimum of 2 days at 22 C.Organelle morphology changes were studied after 5 days of growth at the new temperatures; alterations were most evident at the extremes of 6 and 28 C. The main mitochondrial alteration resulted in changes to the ratio of Type I: Type II organelles; with a decrease in Type I forms away from the optimal range of 20–22 C. Extended culturing at 6 C generated mitochondrial matrical inclusions. Ribosomal attachment to the endoplasmic reticulum, a common feature of 20 C-grown cells, decreased at the temperature extremes, where an increase in free ribosomes occurred. Upon extended culture at 6 C helical structures, usually observed in groups only within the nucleus, were also present in the cytoplasm. Golgi complexes were less common in cells maintained at extreme temperatures and often showed differences in shape. These changes were all reversible on a return to culturing at 20 C.The possible functional significance of these findings is discussed.     

Purification and characterization of (1→3, 1→4)-β-glucan endohydrolases from germinated wheat (Triticum aestivum)

A (13, 14)--glucan 4-glucanohydrolase [(13, 14)--glucanase, EC 3.2.1.73] was purified to homogeneity from extracts of germinated wheat grain. The enzyme, which was identified as an endohydrolase on the basis of oligosaccharide products released from a (13, 14)--glucan substrate, has an apparent pI of 8.2 and an apparent molecular mass of 30 kDa. Western blot analyses with specific monoclonal antibodies indicated that the enzyme is related to (13, 14)--glucanase isoenzyme EI from barley. The complete primary structure of the wheat (13, 14)--glucanase has been deduced from nucleotide sequence analysis of cDNAs isolated from a library prepared using poly(A)⁺ RNA from gibberellic acid-treated wheat aleurone layers. One cDNA, designated LW2, is 1426 nucleotide pairs in length and encodes a 306 amino acid enzyme, together with a NH₂-terminal signal peptide of 28 amino acid residues. The mature polypeptide encoded by this cDNA has a molecular mass of 32085 and a predicted pI of 8.1. The other cDNA, designated LW1, carries a 109 nucleotide pair sequence at its 5 end that is characteristic of plant introns and therefore appears to have been synthesized from an incompletely processed mRNA. Comparison of the coding and 3-untranslated regions of the two cDNAs reveals 31 nucleotide substitutions, but none of these result in amino acid substitutions. Thus, the cDNAs encode enzymes with identical primary structures, but their corresponding mRNAs may have originated from homeologous chromosomes in the hexaploid wheat genome.     

Purification and initial characterization of phycobiliproteins from the endophytic cyanobacterium of Azolla

The endophytic cyanobacterium, Anabaena azollae, isolated from laboratory cultures of Azolla caroliniana Willd., contains three spectroscopically distinct biliproteins. About 70% of the biliprotein is c-phycocyanin (_max 610 nm) and 13% is allophycocyanin (_max 647 nm, shoulder 620 nm). A third pigment corresponds to phycoerythrocyanin (_max 570 nm, shoulder 590 nm). In very dilute solutions of allophycocyanin, at constant pH and buffer strength, the 647 nm maximum disappears and a single _max occurs at 615–620 nm. The 647 nm absorption maximum reappears upon concentrating the dilute solution. Very dilute solutions of phycoerythrocyanin exhibit a broad peak between 570 and 590 nm. Absorption spectra of c-phycocyanin are not significantly altered upon dilution. Fluorescence emission maxima of phycoerythrocyanin, c-phycocyanin, and allophycocyanin occur at 630 nm, 643 nm and 660 nm respectively, using 540 nm excitation. Two subunits, of molecular weight 16,500 () and 20,600 (), are seen in c-phycocyanin upon dissociation with SDS. Dissociation of allophycocyanin and phycoerythrocyanin with SDS yields one sizeclass of subunits, with a molecular weight of about 17,500 for allophycocyanin and 18,000 for phycoerythrocyanin.Contribution No. 684 Offprint requests to: G. A. Peters     

Purification and characterization of aspartate aminotransferase from developing embryos of the camel tick Hyalomma dromedarii

Aspartate transaminase (AST) activity in the camel tick Hyalomma dromedarii was followed throughout embryogenesis. During purification of AST to homogeneity, ion exchange chromatography lead to four separate forms (termed I, II, III and IV). AST II with the highest specific activity was pure after chromatography on Sephacryl S-300. The molecular mass of AST II was 52KDa for the native enzyme, composed of one subunit of 50KDa. AST II had a Km value of 0.67mM for -ketoglutarate and 15.1mM for aspartate. AST II had a pH optimum of 7.5 with heat stability up to 50°C for 15min. The enzyme was activated by MnCl₂, and inhibited by CaCl₂, MgCl₂, NiCl₂, and ZnCl₂.     

Ultrastructure of the nerve-muscle junction in the pharynx of the earthworm,Lumbricus terrestris

Summary InLumbricus terrestris the wall of the pharynx is built up from obliquely striated longitudinal and circular muscle layers. The occurrence of perikarya and nerve bundles showing green fluorescence suggests the presence of aminergic innervation in the pharynx. A significant number of chemical synapses were detected in the neuropil among axon terminals. The junctional gap is generally 100–300 nm wide in type I junctions which resemble the cholinergic motor endplates of vertebrate skeletal muscle. A narrow junctional gap of about 25 nm is characteristic of the close contacts in the type II neuromuscular junction. Agranular spherical vesicles, together with small and large dense-cored granules, fill in these axon terminals.     

Two forms of α-glucosidase from sugar-beet seeds

Two forms of -glucosidase (EC 3.2.1.20), designated as I and II, have been isolated from sugarbeet (Beta vulgaris L.) seeds by a procedure including fractionation with ammonium sulfate and ethanol, carboxymethyl-cellulose column chromatography, and preparative disc gel electrophoresis. The two enzymes were homogeneous by polyacrylamide disc gel electrophoresis. Their molecular weights were 98,000 (I) and 60,000 (II). -Glucosidase I readily hydrolyzed maltose, isomaltose, kojibiose, maltotriose, panose, amylose, soluble starch, amylopectin and glycogen. -Glucosidase II also hydrolyzed maltose, kojibiose and maltotriose but hydrolyzed the other substrates only very weakly or not at all. -Glucosidase I hydrolyzed soluble starch at a faster rate than maltose. It produced isomaltose and panose as the main -glucosyltransfer products from maltose, whereas maltotriose was the main product of -glucosidase II. -Glucosidase I hydrolyzed amylose liberating -glucose. The neutral-sugar content was calculated to be 2.7% for -glucosidase I and 8.8% for -glucosidase II. The main neutral sugar was mannose in -glucosidase I, and glucose in -glucosidase II.     

The response of a cytokinin resistant mutant is highly specific and permits a new cytokinin bioassay

We have previously isolated six independent cytokinin-resistant mutants of Nicotiana plumbaginifolia which define three complementation groups, zeal, zea2 and zea3. We report here the characterization of the phenotypic response to cytokinin treatment of the mutant 1–64, belonging to the zeal group, and the result of the study of the specificity of this response. The phenotype of this mutant grown in the presence of cytokinin concentrations higher than 0.1 M is characterized by a hypertrophy of the cotyledons and hypocotyl which results in an increase of plantlet fresh weight. This hypertrophy is correlated to cytokinin concentration in a range between 0.01 to 10 M. The specificity of this response has been verified by using adenine and urea type cytokinins, as well as enantiomers of methylzeatin and methylbenzyladenine which differ widely in their cytokinin activities. We show that the high specificity of the hypertrophic response to cytokinins can be used as a convenient bioassay to screen the cytokinin activity of adenine or urea type molecules.Abbreviations zeatin [6-(4-hydroxy-3-methylbut-trans-2-enylamino)purine] - iP isopentenyladenine [6-(3-methylbut-2-enylamino)purine] - BA benzyladenine [6-(benzylamino)purine] - (R)-(+)-MeZea [(R)--methylzeatin] - (S)-(–)-MeZea [(S)--methylzeatin] - (R)-(+)-MeBA [(R)--methylbenzyladenine] - (S)-(–)-MeBA [(S)--methylbenzyladenine] - CPPU N-(2-chloro-4-pyridyl)-N-phenylurea - thidiazuron N-(1,2,3-thiadiazol-5-pyridyl)-N-phenylurea The authors dedicate this paper to the memory of Jean-Pierre Bourgin, Director of the Laboratoire de Biologie Cellulaire, who died suddenly on October 29, 1994.     

Fluorescence studies on interaction between phospho-LHC II and subchloroplast Photosystem 1 preparations

Chloroplast proteins were phosphorylated under two test conditions: white light irradiance alone and white light irradiance with the addition of glucose and glucose oxidase, used to produce an anaerobic medium. The interaction of phospho-LHC II with Photosystem 1 (PS 1) was studied for two types of PS I preparation. Changes in the chlorophyll a/b ratio and the ratio of 650 and 680 nm band intensities (E650/E680) in fluorescence excitation spectra were used in calculating the phospho-LHC II portion which became associated with PS 1. It is shown that the associated portion of phospho-LHC II varies for each of the PS 1 preparations and phosphorylation procedures. Possible conclusions as regards the transfer of various sets of LHC II subpopulations under different phosphorylation procedures and the differences of interaction with PS 1 are discussed.Abbreviations PS 1 Photosystem 1 - PS 2 Photosystem 2 - LHC II light-harvesting chlorophyll a/b protein complex II - Chl chlorophyll - fluorescence quantum yield - _f life time of fluorescence at =685 nm - F735 fluorescence band with a maximum at 735 nm - F685 fluorescence band with a maximum at 685 nm - E650/E680 ratio of amplitudes in excitation fluorescence spectrum at 650 and 680 nm     

Fluorescence and reflectance characteristics of manganese deficient soybean leaves: Effects of leaf age and choice of leaflet

Leaf reflectance and fluorescence characteristics of soybean (Glycine max cv Bragg) are influenced strongly by Mn availability. This report evaluates the effects of leaflet choice, leaf age, and leaf nodal position on several spectral characteristics. Leaves were obtained from soybeans grown hydroponically under controlled environmental conditions with wide differences in Mn supply. The ratio of constant yield fluorescence (F_o) to variable yield fluorescence (F_v), the ratios of reflectance at 750 nm to 550 nm and that at 650 nm to 550 nm, the position of the "red edge" near 700 nm, and an index of leaf "yellowness" were measured periodically. Increasing leaf age caused increases in the "red edge" and in both reflectance ratios. Leaf "yellowness" and the fluorescence ratio F_o/F_v decreased with leaf age and increased with leaf nodal position, primarily in Mn deficient leaves. Effects arising from leaf choice were smaller than those caused by Mn deficiency.     

Molecular mapping of a new gene Rrs4 CI 11549 for resistance to barley scald (Rhynchosporium secalis)

Doubled haploid (DH) progeny from a cross between the scald susceptible barley (Hordeum vulgare L.) cultivar Ingrid and the resistant accession CI 11549 (Nigrinudum) was evaluated for resistance in the pathogen Rhynchosporium secalis (Oudem) J.J. Davis. Two linked and incompletely dominant loci confer resistance CI 11549 against isolate 4004. One is an allele at the complex Rrs1 locus on chromosome 3H close to the centromere; the other is located 22 cM distally on the long arm. The latter locus is designated Rrs4. In BC₃-lines into Ingrid from CI 2222 (another Nigrinudum) resistance seems governed by one locus close to the telomeric region of chromosome 7H, probably allelic to Rrs2. In neither case did we find any trace of the recessive gene rh8 reported to be present in Nigrinudum. Various resistance donors of Ethiopian origin designated as Nigrinudum, Jet or Abyssinian were identical to a great extent with respect to markers, but differed in resistance to different isolates of scald or in barley yellow dwarf virus (BYDV) resistance. The implications for their use as differentials in scald tests and screening of germplasm collections are discussed.     

Quantitative estimation of the surface carbohydrates on the infection structures of rust fungi with enzymes and lectins

Lectins of Triticum vulgaris (WGA), Concanavalia ensiformis (ConA), Phaseolus vulgaris (PHA), Lotus tetragonolobus (LTA), Arachis hypogaea (PNA), Ricinus communis (RCA I), Griffonia simplicifolia (GSA II) and the enzymes endo-(13)--D-glucanase, exo-(13)--D-glucanase and laminarinase were tested for binding to the infection structures of Puccinia coronata and Uromyces appendiculatus. The enzymes and lectins were labeled with fluorescein and the fluorescence was measured with a microscope photometer. GSA II and ConA bound to all parts of the two rust fungi to a certain extent. The germ tubes of P. coronata bound at least two times more WGA than did the germ tubes of U. appendiculatus. The appressoria of both rust fungi additionally bound exo-(13)--glucanase, endo-(13)--glucanase and laminarinase. The substomatal vesicle and the infection hypha of both rust fungi mainly bound the glucanases. Furthermore, the substomatal vesicle of U. appendiculatus bound PHA. No obvious binding with LTA, RCA I and PNA was observed. Binding generally could be inhibited by appropriate haptens. Binding to uredospores generally appeared unspecific. The results indicate that the germ tubes have chitin on their outer surfaces, the appressoria chitin and glucans and the substomatal vesicles and infection hyphae mainly glucans. Compared to P. coronata, U. appendiculatus has more terminal linked glucose residues or the glucan has more (13)--linkages. Also, U. appendiculatus has N-acetylgalactosamine or a similar sugar on the surface of the substomatal vesicle.Abbreviations ConA Concanavalia ensiformis agglutinin - FITC fluorescein isothiocyanate - GSA II Griffonia simplicifolic agglutimin II - LTA Lotus tetragonolobus agglutinin - PBS phosphate buffered saline - PNA Peanut agglutinin - RCA I Ricinus communis agglutinin I - PHA Phaseolus vulgaris agglutinin - WGA Wheat germ agglutinin     

Spectral characteristics of phytochrome in vivo and in vitro

The absorption maximum of the far-red absorbing form of phytochrome in the difference spectrum for phototransformation (Pfr max) was investigated in vivo and in in vitro pellets from dark grown Hordeum vulgare L. primary leaves. Exposure of pellets in Honda medium from tissue pre-irradiated with red light to far red light gave a Pfr max of 734 nm, a slightly longer wavelength than was seen in vivo (730 nm). After incubation as the red absorbing form of phytochrome (Pr) for 2 h at 0° C irradiation with red light showed that Pfr max had shifted to shorter wavelength (716 nm) in Honda medium. Further incubation as Pfr for 2 h at 0° C and irradiation with far red light showed that Pfr max had shifted to longer wavelength (726 nm). Similar shifts were also seen in other media, although the peak positions were different. Phytochrome remained pelletable throughout these experiments and Pfr max is compared to that of soluble phytochrome in similar media. The results are interpreted as indicating changes in molecular environment of the putative phytochrome membrane receptor site and that Pfr max can be used to probe the nature of this binding.Abbreviations D Dark - EDTA Ethylene diamine tetra-acetic acid - F far red light - MOPS N-morpholino-3-propane-sulphonic acid - P Phytochrome - Pr red absorbing form of P - Pfr far red absorbing form of P - Pfr max wavelength maximum of Pfr absorbance in a phototransformation difference spectrum - R red light     

Characterization of the biliproteins of Gloeobacter violaceus chromophore content of a cyanobacterial phycoerythrin carrying phycourobilin chromophore

The biliproteins of the unicellular, thylakoid-less cyanobacterium Gleobacter violaceus were resolved by chromatography on hydroxylapatite and DEAE-cellulose into five components: phycoerythrin I and II, phycocyanin I and II, and allophycocyanin. Allophycocyanin B was not detected. Three of these components, phycoerythrin II, phycocyanin II, and allophycocyanin, were purified to homogeneity. Phycoerythrin II crystallized as hexagonal prisms. G. violaceus allophycocyanin crystallized as thin plates; unter similar conditions other cyanobacterial allophycocyanins crystallize as needles. The biliproteins in the phycoerythrin I and phycocyanin I components were present in polydisperse, high molecular weight aggregates, which may represent incompletely dissociated substructures of the phycobilisome.Both phycoerythrin components from G. violaceus carry phycoerythrobilin and phycourbilin groups in the ratio of 6:1. Separation of the and subunits of these biliproteins revealed that the phycoerythrobilins were equally distributed between the two subunits, and that the subunit alone carried the phycourobilin. These phycoerythrins are the first cyanobacterial phycobiliproteins found to carry a phycourobilin prosthetic group.Abbreviations used PE poycoerythrin - PC phycocyanin - AP allophycocyanin - SDS sodium dodecyl sulfate - PAGE polyacrylamide gel electrophoresis - B Bangiophycean - R Rhodophytan - C Cyanobacterial