Molecular Genetics and Genomics

, Volume 271, Issue 1, pp 40–49 | Cite as

LexA-binding sequences in Gram-positive and cyanobacteria are closely related

  • G. Mazón
  • J. M. Lucena
  • S. Campoy
  • A. R. Fernández de Henestrosa
  • P. Candau
  • J. Barbé
Original Paper


The lexA gene of the cyanobacterium Anabaena sp. strain PCC7120 has been cloned by PCR amplification with primers designed after TBLASTN analysis of its genome sequence using the Escherichia coli LexA sequence as a probe. After over-expression in E. coli and subsequent purification, footprinting experiments demonstrated that the Anabaena LexA protein binds to the sequence TAGTACTAATGTTCTA, which is found upstream of its own coding gene. Directed mutagenesis and sequence comparison of promoters of other Anabaena genes, as well as those of several cyanobacteria, allowed us to define the motif RGTACNNNDGTWCB as the LexA box in this bacterial phylum. Substitution of a single nucleotide in this motif present in the Anabena lexA promoter is sufficient to enable it to bind the Bacillus subtilis LexA protein. These data indicate that Cyanobacteria and Gram-positive bacteria are phylogenetically closely related.


Lex A box SOS response Cyanobacteria Bacterial phylogeny 



This work was funded by Grants BMC2001-2065 from the Ministerio de Ciencia y Tecnología (MCyT) de España, 2001SGR-206 from the Departament d’Universitats, Recerca i Societat de la Informació (DURSI) de la Generalitat de Catalunya and CVI-112 from the Junta de Andalucía. Antonio R. Fernández de Henestrosa and Gerard Mazón were recipients of a postdoctoral contract and a predoctoral fellowship from the MCyT, respectively. We are deeply indebted to Dr. Roger Woodgate for his generous gift of the B. subtilis LexA protein. We also wish to acknowledge Dr. Pilar Cortés, Joan Ruiz and Susana Escribano for their excellent technical assistance. We are grateful to Prof. R. S. Gupta and Prof. R. Guerrero for their critical reading of the manuscript


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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • G. Mazón
    • 1
  • J. M. Lucena
    • 2
  • S. Campoy
    • 3
  • A. R. Fernández de Henestrosa
    • 1
    • 4
  • P. Candau
    • 2
  • J. Barbé
    • 1
  1. 1.Departament de Genètica i MicrobiologiaUniversitat Autònoma de BarcelonaBarcelonaSpain
  2. 2.Instituto de Bioquímica Vegetal y FotosíntesisUniversidad de Sevilla-CSICSevillaSpain
  3. 3.Institut de Recerca i Tecnologia Agroalimentària (UAB-IRTA), Centre de Recerca en Sanitat Animal (CReSA)Universitat Autònoma de BarcelonaBarcelonaSpain
  4. 4.Centro de Biología Molecular Severo Ochoa (CSIC)MadridSpain

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