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  • Calothrix sp. PCC 7601  (1)
  • Photosynthesis  (1)
  • lac promoters  (1)
  • 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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    Paper (German National Licenses)
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  • 2
    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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    Paper (German National Licenses)
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  • 3
    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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    Paper (German National Licenses)
    Fulltext
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