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  • 1
    Electronic Resource
    Electronic Resource
    The structure of cyanobacterial phycobilisomes: a model (1979)
    Springer
    Archives of microbiology 123 (1979), S. 113-127 
    Details
    ISSN: 1432-072X
    Keywords: Phycobilisomes ; Phycobiliproteins ; Cyanobacteria ; Chromatic adaptation ; Fine structure ; Photosynthesis ; Protein assembly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phycobilisomes, supramolecular complexes of water-soluble accessory pigments, serve as the major light-harvesting antennae in cyanobacteria and red algae. Regular arrays of these organelles are found on the surface of the thylakoid membranes of these organisms. In the present study, the hemi-discoidal phycobilisomes of several species of cyanobacteria were examined in thin sections of cells and by negative staining after isolation and fixation. Their fundamental structures were found to be the same. Isolated phycobilisomes possessed a triangular core assembled from three stacks of disc-shaped subunits. Each stack contained two discs which were ∼12 nm in diameter and ∼6–7 nm thick. Each of these discs was probably subdivided into halves ∼3–3.5 nm thick. Radiating from each of two sides of the triangular core were three rods ∼12 nm in diameter. Each rod consisted of stacks of 2 to 6 disc-shaped subunits ∼6 nm thick. These discs were subdivided into halves ∼3 nm thick. The average number of discs of ∼6 nm thickness forming the peripheral rods varied among the strains studied. For certain chromatically adapting strains, the average rod length was dependent upon the wavelength of light to which cells were exposed during growth. Analyses of phycobilisomes by spectroscopic techniques, polyacrylamide gel electrophoresis, and electron microscopy were compared. These analyses suggested that the triangular core was composed of allophycocyanin and that the peripheral rods contained phycocyanin and phycoerythrin (when present). A detailed model of the hemi-discoidal phycobilisome is proposed. This model can account for many aspects of phycobiliprotein assembly and energy transfer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00446810
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  • 2
    Electronic Resource
    Electronic Resource
    Modification of the pII protein in response to carbon and nitrogen availability in filamentous heterocystous cyanobacteria (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 144 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract In the filamentous cyanobacterium Calothrix PCC 7504, which fixes N2 aerobically, the modification state of the regulatory PII protein (GlnB) was shown to depend on nitrogen and carbon availability, as observed in the unicellular non-fixing strain Synechococcus PCC 7942. However, the conditions for modifications, the time dependence of the process and the electrophoretic behavior of the native PII isoforms differed somewhat between the two strains. In another strain, Calothrix PCC 7601, which has lost the capability to fix N2, PII was modified only if ammonia plus an inhibitor of glutamine synthetase were present. It is proposed that: (i) the behavior of the PII proteins depends upon the physiological properties of the strains; and (ii) the modification system of PII per se may differ between the two cyanobacterial genera.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08528.x
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  • 3
    Electronic Resource
    Electronic Resource
    Co-ordinated expression of phycobiliprotein operons in the chromatically adapting cyanobacterium Calothrix PCC 7601: a role for RcaD and RcaG (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 43 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In the cyanobacterium Calothrix sp. PCC 7601 the cpc2 operon encoding phycocyanin 2 (PC2) is expressed if red radiations are available. RcaD was previously identified in extracts from red-light-grown cells as an alkaline phosphatase-sensitive protein that binds upstream of the transcription start point (TSP) of the cpc2 operon. In this work, RcaD was purified, and the corresponding gene cloned with a PCR probe obtained using degenerated primers based on RcaD peptide sequences (accession no. AJ319541). Purified RcaD binds to the cpc2 promoter region and also to those of the constitutive cpc1 and apc1 operons that encode phycocyanin 1 and allophycocyanin. Escherichia coli-overexpressed RcaD can bind to the cpc2 promoter region. The rcaD gene is upstream of an open reading frame (ORF) termed rcaG. Co-transcription of both genes was demonstrated by reverse transcription (RT)-PCR experiments, and found to be independent of the light wavelengths. A single TSP was mapped. Sequence features of RcaD and RcaG led us to propose a functional relationship between these two proteins. A rcaD mutant generated by allelic exchange exhibited altered expression of the cpc2, cpeBA, apc1 and cpc1 operons upon green to red-light shifts. RcaD seems to be a co-activator co-ordinating the transcription of the phycobiliprotein operons upon changes in light spectral quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02783.x
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  • 4
    Electronic Resource
    Electronic Resource
    A phosphorylated DNA-binding protein is specific for the red-light signal during complementary chromatic adaptation in cyanobacteria (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 13 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Complementary chromatic adaptation is a mechanism by which some cyanobacteria that are able to synthesize phycoerythrin can adapt their pigment (phycobili-protein) content to the incident wavelengths of the light. In Calothrix sp. PCC 7601 it concerns phycoerythrin (cpe operon), synthesized under green light, and phycocyanin-2 (cpc2 operon), expressed under red light, and involves transcriptional controls. With cell-free extracts from Calothrix sp. PCC 7601 grown under various light regimes, a protein designated RcaD was found by gel retardation experiments to specifically bind to the cpc2 promoter region and to be present only in red-light-grown cells. This protein was partially purified and its binding activity was shown to be sensitive to an alkaline phosphatase treatment. RcaO can protect two regions of the cpc2 promoter sequence against degradation by DNase I. Because its activity is detected only under the conditions required for cpc2 expression, we propose that RcaD is a positive effector of transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00479.x
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  • 5
    Electronic Resource
    Electronic Resource
    Specific initiation of transcription at a cyanobacterial promoter with RNA polymerase purified from Calothrix sp. PCC 7601 (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 13 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Although in cyanobacteria many genes have been shown to be transcriptionally controlled by specific stimuli, little is known about promoter structure and the form of RNA polymerase that recognizes individual promoters. RNA polymerase holoenzyme has been purified from Calothrix sp. PCC 7601. its polypeptide composition resembles that of the plant chloroplast enzymes. To study transcription in cyanobacteria further, we have analysed the promoter-recognition properties of the purified enzyme. In vitro transcription was assayed with the promoter of the phycocyanin gene (cpc1) that is expressed whatever the incident light conditions. Transcription initiation at the same start point as in vivo was obtained with the Calothrix sp. PCC 7601 purified enzyme and the Escherichia coli core enzyme supplemented with a Calothrix sp. PCC 7601 sigma factor, but not with the E. coli holoenzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00480.x
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  • 6
    Electronic Resource
    Electronic Resource
    Photoregulation of gene expression in the filamentous cyanobacterium Calothrix sp. PCC 7601: light-harvesting complexes and cell differentiation (1988)
    Springer
    Photosynthesis research 18 (1988), S. 99-132 
    Details
    ISSN: 1573-5079
    Keywords: Calothrix sp. PCC 7601 ; gas vesicles ; hormogonia ; photoregulation ; phycobiliproteins ; phycobilisomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light plays a major role in many physiological processes in cyanobacteria. In Calothrix sp. PCC 7601, these include the biosynthesis of the components of the light-harvesting antenna (phycobilisomes) and the differentiation of the vegetative trichomes into hormogonia (short chains of smaller cells). In order to study the molecular basis for the photoregulation of gene expression, physiological studies have been coupled with the characterization of genes involved either in the formation of phycobilisomes or in the synthesis of gas vesicles, which are only present at the hormogonial stage. In each system, a number of genes have been isolated and sequenced. This demonstrated the existence of multigene families, as well as of gene products which have not yet been identified biochemically. Further studies have also established the occurrence of both transcriptional and post-transcriptional regulation. The transcription of genes encoding components of the phycobilisome rods is light-wavelength dependent, while translation of the phycocyanin genes may require the synthesis of another gene product irrespective of the light regime. In this report, we propose two hypothetical models which might be part of the complex regulatory mechanisms involved in the formation of functional phycobilisomes. On the other hand, transcription of genes involved in the gas vesicles formation (gvp genes) is turned on during hormogonia differentiation, while that of phycobiliprotein genes is simultaneously turned off. In addition, and antisense RNA which might modulate the translation of the gvp mRNAs is synthezised.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00042981
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  • 7
    Electronic Resource
    Electronic Resource
    Promoter recognition by a cyanobacterial RNA polymerase: in vitro studies with the Calothrix sp. PCC 7601 transcriptional factors RcaA and RcaD (1998)
    Springer
    Plant molecular biology 36 (1998), S. 649-659 
    Details
    ISSN: 1573-5028
    Keywords: complementary chromatic adaptation ; in vitro transcription ; lac promoters ; RcaA ; transcription factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To study the transcriptional apparatus and the mechanisms that control gene expression in cyanobacteria, the RNA polymerase was purified from the filamentous Calothrix sp. PCC 7601 and used in in vitro transcription assays. Conditions required for specific transcription initiation to occur were analyzed with the eleven Calothrix PCC 7601 genes for which the 5′ ends have been mapped. Most of the transcripts directly obtained did not have the expected size, providing a test for looking at specific transcription factors. Addition of RcaA, a protein that binds to the promoter region of the phycobiliprotein cpeBA operon, restored accurate initiation of transcription in the in vitro system for three phycobiliprotein promoters. RcaA thus is a transcription factor that allows to mimick in vivo transcription. In parallel, the functional properties of the Escherichia coli and cyanobacterial RNA polymerases were compared. The enteric enzyme could not precisely initiate transcription at the promoter of a phycobiliprotein gene and, reciprocally, the cyanobacterial RNA polymerase could initiate transcription at PlacUV5, but not from wild-type Plac promoters. The different behaviours of the enzymes are discussed in the light of the structural differences that exist between subunits of the RNA polymerases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005983320006
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  • 8
    Electronic Resource
    Electronic Resource
    A multigene family in Calothrix sp. PCC 7601 encodes phycocyanin, the major component of the cyanobacterial light-harvesting antenna (1988)
    Springer
    Molecular genetics and genomics 211 (1988), S. 296-304 
    Details
    ISSN: 1617-4623
    Keywords: Complementary chromatic adaptation ; Gene expression ; Photoregulation ; Phycobilisome ; Recombinant DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In cyanobacteria, light is harvested by phycobilisomes which are essentially made up of chromophoric proteins called phycobiliproteins. We have characterized two gene clusters (cpcB1, cpcA1 and cpcB3, cpcA3) each encoding the two subunits of phycocyanin (βPC and αPC, respectively), one of the major phycobiliproteins in Calothrix 7601. Downstream from the gene encoding the PCα subunit in cluster 1, an open reading frame was found, cpcE1. These genes are organized in two transcriptional units, namely: cpcB3 A3 and cpcB1 A1 E1. All these genes are transcribed whatever the chromatic light received during cell growth. Consequently, although only one type of “constitutive” PC has been biochemically characterized, we have demonstrated that there are two cpc operons “constitutively” transcribed in this strain. With the previously described red light “inducible” cpcB2 A2 operon, there are three copies of the PC encoding genes in Calothrix 7601. The significance of this newly described multigene family in cyanobacteria is discussed. We have also mapped the 5′ and 3′ termini of the major transcript from the cpc1 operon. Analysis of the 5′ untranslated region of this transcript has revealed alternative secondary structures which are proposed to play a role in the regulation of the expression of this operon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330607
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