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  • 1
    Electronic Resource
    Electronic Resource
    Influence of cesium on tetrapyrrole biosynthesis in etiolated and greening barley leaves (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 99 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Cesium chloride (CsCl) treatment of greening primary leaves of barley for 8 h inhibited chlorophyl] accumulation in a concentration-dependent manner and led to the accumulation of excessive amounts of uroporphyrin(ogen) III (URO[gen]) and to a minor extent of heptacarboxylporphyrin(ogen). When dark-grown leaves were incubated with CsCl, accumulation of URO(gen) was observed only after feeding of the tetrapyrrole precursor 5-aminolevulinic acid. Western blot analysis showed no apparent difference in content of uroporphyrinogen decarboxylase (EC 4.1.1.37, UROD) or selected proteins involved in tetrapyrrole biosynthesis in extracts of CsCl-incubated (15 mM) versus control leaves. UROD activity was drastically decreased upon CsCl treatment in leaves incubated in the dark or in the light (44 and 86%, respectively). Selected preceding enzymes of the tetrapyrrole biosynthetic pathway, 5-aminolevulinic acid dehydratase (EC 4.2.1.24, ALAD) and porphobilinogen deaminase (EC 4.3.1.8, PBGD), were influenced only to a minor extent under standard incubation conditions (15 mM CsCl). Furthermore, the ALA synthesizing capacity did not differ in leaves incubated with and without Cs− cations. UROD activity of crude homogenates from control plants and after partial purification was reduced to 56 and 80%, respectively, upon addition of 10 mM CsCl. Equal concentrations of KCl were not inhibitory. Enzyme assays of the same barley extract in the presence of CsCl yielded no effect on ALAD and a minor loss of PBGD activity. The initial visible cytotoxic effect of CsCl appeared to be a selective inhibition of UROD resulting in accumulation of photosensitizing URO (gen). Consequences of the diminished UROD activity on early steps of the tetrapyrrole biosynthesis and its functional and regulatory significance for the porphyrin synthesis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb03444.x
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  • 2
    Electronic Resource
    Electronic Resource
    Gabaculine resistance of Synechococcus glutamate 1-semialdehyde aminotransferase (1992)
    s.l. : American Chemical Society
    Biochemistry 31 (1992), S. 4122-4127 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00131a031
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  • 3
    Electronic Resource
    Electronic Resource
    Glutamate 1-semialdehyde aminotransferase: anomalous enantiomeric reaction and enzyme mechanism (1992)
    s.l. : American Chemical Society
    Biochemistry 31 (1992), S. 11249-11254 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00160a041
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  • 4
    Electronic Resource
    Electronic Resource
    Tobacco uroporphyrinogen-III decarboxylase: characterization, crystallization and preliminary X-ray analysis (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 1709-1711 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Uroporphyrinogen-III decarboxylase from Nicotiana tabacum is a plastidial enzyme involved in the biosynthesis of chlorophyll and haem. Sedimentation equilibrium with protein producing diffracting crystals clearly indicates that the enzyme is a homodimer under similar ionic strength conditions to those found in the chloroplast stroma. Additionally, dynamic light scattering reveals an ionic strength dependence for this oligomerization state. Crystals were obtained in the hexagonal space group P622 with one molecule per asymmetric unit and diffracted to 2.3 Å resolution using synchrotron radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444901013361
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  • 5
    Electronic Resource
    Electronic Resource
    Developmental and circadian control of the capacity for δ-aminolevulinic acid synthesis in green barley (1997)
    Springer
    Planta 202 (1997), S. 235-241 
    Details
    ISSN: 1432-2048
    Keywords: Key words:δ-Aminolevulinate synthesis ; Chlorophyll biosynthesis ; Chloroplast development ; Circadian rhythm ; Hordeum (chlorophyll biosynthesis) ; Pigment protein assembly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The synthesis of δ-aminolevulinic acid (δ-ALA) is a key step in the regulation of tetrapyrrole synthesis. To study the developmentally and circadian-clock controlled mechanism that co-ordinates synthesis of chlorophylls and chlorophyll-binding proteins, δ-ALA-synthesising capacity was analysed in barley (Hordeum vulgare L.) primary leaves grown under dark/light or constant light conditions. The δ-ALA-forming activity oscillated within 24 h with a maximum at the transition of dark to light and a minimum 12 h later, indicating the involvement of the circadian oscillator during development. The capacity for δ-ALA synthesis increased transiently in the middle of barley primary leaves. The δ-ALA-forming-activity correlated well with the previously published steady-state level of mRNA for light-harvesting chlorophyll-binding proteins in space and time; this supports the view of a co-ordinate synthesis of chlorophyll and pigment-binding proteins. Steady-state levels of mRNAs encoding the three enzymes of the δ-ALA-synthesising pathway and of proteins for glutamyl-tRNA reductase (GluTR) and glutamate 1-semialdehyde aminotransferase (GSA AT; EC 5.4.3.8) were analysed for their developmental and circadian expression in barley leaves. The contents of GluTR mRNA and protein cycled parallel to the changes in δ-ALA-forming activity. The levels of GSA AT mRNA oscillated in an opposite phase, but the protein content did not show substantial oscillation under diurnal and circadian growth conditions. No circadian oscillation was detected for glutamyl tRNA synthase (GluRS; EC 6.1.1.17). Maximal GluTR mRNA content and protein was observed in the middle (segments 3 and 4) of the barley primary leaves. The developmentally controlled expression of GluTR therefore differs from that of GSA AT and GluRS, but resembles the capacity for δ-ALA synthesis in a barley leaf gradient. These data indicate that the oscillating, light-dependent and spatial expression of GluTR mRNA might contribute to the regulated formation of the chlorophyll precursor δ-ALA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050124
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  • 6
    Electronic Resource
    Electronic Resource
    Expression studies in tetrapyrrole biosynthesis: inverse maxima of magnesium chelatase and ferrochelatase activity during cyclic photoperiods (1999)
    Springer
    Planta 208 (1999), S. 264-273 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Chlorophyll ; Chloroplast ; Circadian rhythm ; Heme ; Nicotiana (tetrapyrroles) ; Pigment synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The synthesis of tetrapyrroles is regulated in anticipation of rhythmic changes in environmental conditions such as light intensity and temperature. To assess the control of the rate-limiting steps of the metabolic flow as well as the distribution of precursors for chlorophyll and heme synthesis, RNA steady-state levels and activities of enzymes involved in tetrapyrrole biosynthesis were analysed from 4-week-old tobacco (Nicotiana tobacum L.) plants grown under photoperiodically changing conditions. The kinetics of RNA levels and the enzyme activities were compared with those from plants which grew subsequent to the light/dark cycles for 48 h under constant light or dark conditions. The analysis revealed that the two peak activities for 5-aminolevulinic acid synthesis and of magnesium-protoporphyrin IX chelatase (Mg-chelatase) corresponded with the highest accumulation of the transcripts encoding glutamyl-tRNA reductase and CHL H, a subunit of Mg-chelatase, in the first half of the light period during a light/dark cycle. The activity of ferrochelatase (Fe-chelatase) and the level of its RNA showed a maximum just at the transition from light to dark and oscillated with a phase approximately opposite to that of Mg-chelatase activity. The control of 5-aminolevulinic acid synthesis and of the allocation of protoporphyrin IX to Mg- or Fe-chelatase probably reflect the functional coordination of tetrapyrrole biosynthesis in response to daily fluctuations in tetrapyrrole requirements. It is suggested that the coordination of expression and enzyme activities allows, in the light phase, an extensive flow of substrates into the chlorophyll-synthesizing branch of the metabolic pathway and, after the transition from light to dark, a channeling into the heme biosynthetic pathway. Implications for feedback control in the pathway are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050558
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  • 7
    Electronic Resource
    Electronic Resource
    Isolation, sequencing and expression of cDNA sequences encoding uroporphyrinogen decarboxylase from tobacco and barley (1995)
    Springer
    Plant molecular biology 28 (1995), S. 245-256 
    Details
    ISSN: 1573-5028
    Keywords: barley ; chlorophyll biosynthesis ; chloroplast ; expression ; haem biosynthesis ; hemE ; regulation ; tobacco ; uroporphyrinogen decarboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have cloned and sequenced a full-length cDNA for uroporphyrinogen decarboxylase (UROD, EC 4.1.1.37) from tobacco (Nicotiana tabacum L.) and a partial cDNA clone from barley (Hordeum vulgare L.). The cDNA of tobacco encodes a protein of 43 kDa, which has 33% overall similarity to UROD sequences determined from other organisms. We propose that tobacco UROD has an N-terminal extension of 39 amino acid residues. This extension is most likely a chloroplast transit sequence. The in vitro translation product of UROD was imported into pea chloroplasts and processed to ca. 39 kDa. A truncated cDNA, from which the putative transit peptide had been deleted, was used to over-express the mature UROD in Escherichia coli. Purified protein showed UROD activity, thus providing an adequate source for subsequent enzymatic characterization and inhibition studies. Expression of UROD was investigated by northern and western blot analysis during greening of etiolated barley seedlings, and in segments of barley primary leaves grown under day/night cycles. The amount of RNA and protein increased during illumination Maximum UROD-RNA levels were detected in the basal segments relative to the top of the leaf.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020244
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  • 8
    Electronic Resource
    Electronic Resource
    Transiently expressed early light-inducible thylakoid proteins share transmembrane domains with light-harvesting chlorophyll binding proteins (1989)
    Springer
    Plant molecular biology 13 (1989), S. 583-593 
    Details
    ISSN: 1573-5028
    Keywords: early-light ; inducible proteins ; barley ; chloroplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The early light-inducible proteins (ELIPs) of barley chloroplasts are encoded in two multigene families yielding end products of different molecular mass. Sequencing of complete cDNA clones showed that the low and high molecular mass proteins differ by the presence or absence of a 65 amino acid peptide in the amino-terminal part of the mature proteins. Two domains of the ELIPs reveal striking similarity in amino acid sequence with two transmembrane domains of all known light-harvesting chlorophyll a/b-binding proteins from photosystem I and II and may be of importance in anchoring the polypeptides in the membrane. The cDNA sequences of two low molecular mass ELIPs differ by an insert of 5 codons in the putative transit peptide. By in vitro transcription and translation of the cloned DNA and subsequent transport of the products into chloroplasts it could be established that the two precursors are processed into products of identical apparent molecular mass. In vitro translated ELIPs were incorporated into thylakoid membranes both as precursors and mature polypeptides. It is suggested that ELIPs are pigment-free substitutes for light-harvesting polypeptides in the assembly of photosynthetic units during early development of thylakoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027318
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  • 9
    Electronic Resource
    Electronic Resource
    Coproporphyrinogen III oxidase from barley and tobacco — sequence analysis and initial expression studies (1995)
    Springer
    Planta 196 (1995), S. 796-803 
    Details
    ISSN: 1432-2048
    Keywords: 5-Aminolevulinate synthesis ; Chlorophyll synthesis ; Chloroplast (development) ; Hordeum ; Nicotiana ; Tetrapyrrole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Coproporphyrinogen III oxidase (coprogen oxidase; EC 1.3.3.3) is part of the pathway from 5-aminolevulinate to protoporphyrin IX which is common in all organisms and catalyses oxidative decarboxylation at two tetrapyrrole side chains. We cloned and sequenced fulllength cDNAs encoding coprogen oxidase from barley (Hordeum vulgare L.) and tobacco (Nicotiana tabacum L.). They code for precursor peptides of 43.6 kDa and 44.9 kDa, respectively. Import into pea plastids resulted in a processed tobacco protein of approx. 39 kDa, which accumulated in the stroma fraction. Induction of synthesis of recombinant putative tobacco mature coprogen oxidase consisting of 338 amino-acid residues in Escherichia coli at 20°C result in a catalytically active protein of approx. 39 kDa, while induction of its formation at 37°C immediately terminated bacterial growth, possibly due to toxic effects on the metabolic balance of tetrapyrrole biosynthesis. The plant coprogen oxidase gene was expressed to different extents in all tissues investigated. This is most likely due to the differing requirements for tetrapyrroles in different organs. The steady-state level of mRNA did not significantly differ in etiolated and greening barley leaves. The content of coprogen oxidase RNA reached its maximum in developing cells and decreased drastically when cells were completely differentiated. Functioning of the two photosystems apparatus requires the synthesis of all pigment and protein components during plant development. It is speculated that the enzymes involved in tetrapyrrole synthesis are developmentally rather than light-dependently regulated. Regulation of these enzymes also guarantees a constant flux of metabolic intermediates and avoids photodynamic damage by accumulating porphyrins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197347
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  • 10
    Electronic Resource
    Electronic Resource
    Coproporphyrinogen III oxidase from barley and tobacco — sequence analysis and initial expression studies (1995)
    Springer
    Planta 196 (1995), S. 796-803 
    Details
    ISSN: 1432-2048
    Keywords: 5-Aminolevulinate synthesis ; Chlorophyll synthesis ; Chloroplast (development) ; Hordeum ; Nicotiana ; Tetrapyrrole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Coproporphyrinogen III oxidase (coprogen oxidase; EC 1.3.3.3) is part of the pathway from 5-aminolevulinate to protoporphyrin IX which is common in all organisms and catalyses oxidative decarboxylation at two tetrapyrrole side chains. We cloned and sequenced fulllength cDNAs encoding coprogen oxidase from barley (Hordeum vulgare L.) and tobacco (Nicotiana tabacum L.). They code for precursor peptides of 43.6 kDa and 44.9 kDa, respectively. Import into pea plastids resulted in a processed tobacco protein of approx. 39 kDa, which accumulated in the stroma fraction. Induction of synthesis of recombinant putative tobacco mature coprogen oxidase consisting of 338 amino-acid residues inEscherichia coli at 20°C result in a catalytically active protein of approx. 39 kDa, while induction of its formation at 37°C immediately terminated bacterial growth, possibly due to toxic effects on the metabolic balance of tetrapyrrole biosynthesis. The plant coprogen oxidase gene was expressed to different extents in all tissues investigated. This is most likely due to the differing requirements for tetrapyrroles in different organs. The steady-state level of mRNA did not significantly differ in etiolated and greening barley leaves. The content of coprogen oxidase RNA reached its maximum in developing cells and decreased drastically when cells were completely differentiated. Functioning of the two photosystems apparatus requires the synthesis of all pigment and protein components during plant development. It is speculated that the enzymes involved in tetrapyrrole synthesis are developmentally rather than light-dependently regulated. Regulation of these enzymes also guarantees a constant flux of metabolic intermediates and avoids photodynamic damage by accumulating porphyrins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01106776
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