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Gene Review

glnA  -  glutamate--ammonia ligase

Nostoc sp. PCC 7120

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Disease relevance of glnA

  • This site showed extensive sequence similarity with the promoter region of glnA from Synechococcus sp. strain PCC 7942 [1].
  • A transcription start point of the Anabaena glnA gene (corresponding to RNAl), that has been shown to be used preferentially after nitrogen step-down, was not used in the ntcA insertional mutant [2].
  • A Synechocystis sp. glnA mutant could not be obtained, however, from the wild-type Synechocystis sp. The Anabaena glutamine synthetase enzyme was subject to ammonium-promoted inactivation when expressed in the Synechocystis strain but not in the Anabaena strain itself [3].
  • In the filamentous, N(2)-fixing cyanobacterium Anabaena sp. strain PCC 7120, glnA is expressed from multiple promoters that generate several transcripts whose abundance is influenced by NtcA, the transcription factor exerting global nitrogen control in cyanobacteria [4].
  • Molecular characteristics of glnA linked mutations in the nitrogen-fixing cyanobacterium Nostoc muscorum [5].

High impact information on glnA


Chemical compound and disease context of glnA

  • The glutamine synthetase (GS)-impaired mutants of Nostoc muscorum, isolated as ethylenediamine (EDA) resistant phenotype, were characterized for glnA linked processes to investigate the molecular mechanism of GS impairment [5].

Biological context of glnA

  • Morphological analyses revealed differences between the free-living isolates and their symbiotic counterparts, as did restriction fragment length polymorphism (RFLP) analyses with both single-copy glnA and rbcS gene probes and a multicopy psbA gene probe [7].
  • Results suggested that point mutation(s) inflicted in glnA gene of N. muscorum are responsible for differential production of catalytically modified GS in EDA-resistant phenotypes [5].

Other interactions of glnA

  • Northern analysis of RNA samples isolated from ammonium-grown cultures of the ntcA mutant showed reduced amounts of glnA message and the absence of a 1.7-kb transcript [8].
  • We also show that the levels of these psbB gene transcripts as well as those of the glnA, rbcLS, and psbA genes, in RNA prepared from whole filaments, remain constant during heterocyst differentiation [9].
  • Using the Southern blot technique and cloned Anabaena PCC 7120 nifK and glnA genes as probes, restriction fragment length polymorphisms of these cyanobacterial symbionts were compared [10].

Analytical, diagnostic and therapeutic context of glnA

  • Northern blot analysis indicated differential levels of GS specific mRNA and abundance of glnA transcripts of 1.7 and 1.9 kb in the mutant strains [5].


  1. GlbN (cyanoglobin) is a peripheral membrane protein that is restricted to certain Nostoc spp. Hill, D.R., Belbin, T.J., Thorsteinsson, M.V., Bassam, D., Brass, S., Ernst, A., Böger, P., Paerl, H., Mulligan, M.E., Potts, M. J. Bacteriol. (1996) [Pubmed]
  2. Requirement of the regulatory protein NtcA for the expression of nitrogen assimilation and heterocyst development genes in the cyanobacterium Anabaena sp. PCC 7120. Frías, J.E., Flores, E., Herrero, A. Mol. Microbiol. (1994) [Pubmed]
  3. Regulation of Anabaena sp. strain PCC 7120 glutamine synthetase activity in a Synechocystis sp. strain PCC 6803 derivative strain bearing the Anabaena glnA gene and a mutated host glnA gene. Mérida, A., Flores, E., Florencio, F.J. J. Bacteriol. (1992) [Pubmed]
  4. The NtcA-dependent P1 promoter is utilized for glnA expression in N2-fixing heterocysts of Anabaena sp. strain PCC 7120. Valladares, A., Muro-Pastor, A.M., Herrero, A., Flores, E. J. Bacteriol. (2004) [Pubmed]
  5. Molecular characteristics of glnA linked mutations in the nitrogen-fixing cyanobacterium Nostoc muscorum. Srivastava, R., Amla, D.V. Curr. Microbiol. (2002) [Pubmed]
  6. Two Anabaena sp. strain PCC 7120 DNA-binding factors interact with vegetative cell- and heterocyst-specific genes. Ramasubramanian, T.S., Wei, T.F., Golden, J.W. J. Bacteriol. (1994) [Pubmed]
  7. Identification of a common cyanobacterial symbiont associated with Azolla spp. through molecular and morphological characterization of free-living and symbiotic cyanobacteria. Gebhardt, J.S., Nierzwicki-Bauer, S.A. Appl. Environ. Microbiol. (1991) [Pubmed]
  8. Anabaena sp. strain PCC 7120 ntcA gene required for growth on nitrate and heterocyst development. Wei, T.F., Ramasubramanian, T.S., Golden, J.W. J. Bacteriol. (1994) [Pubmed]
  9. Isolation, sequence and transcription of the gene encoding the photosystem II chlorophyll-binding protein, CP-47, in the cyanobacterium Anabaena 7120. Lang, J.D., Haselkorn, R. Plant Mol. Biol. (1989) [Pubmed]
  10. Comparison of DNA restriction fragment length polymorphisms of Nostoc strains in and from cycads. Lindblad, P., Haselkorn, R., Bergman, B., Nierzwicki-Bauer, S.A. Arch. Microbiol. (1989) [Pubmed]
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