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Glutamine synthetase stabilizes the binding of GlnR to nitrogen fixation gene operators
Author(s) -
Fernandes Gabriela de C.,
Hauf Ksenia,
Sant'Anna Fernando H.,
Forchhammer Karl,
Passaglia Luciane M. P.
Publication year - 2017
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.14021
Subject(s) - gene , glutamine synthetase , glutamine , biology , diazotroph , binding site , biochemistry , genetics , nitrogen fixation , amino acid , bacteria
Biological nitrogen fixation ( BNF ) is a high energy demanding process carried out by diazotrophic microorganisms that supply combined nitrogen to the biosphere. The genes related to BNF are strictly regulated, but these mechanisms are poorly understood in gram‐positive bacteria. The transcription factor GlnR was proposed to regulate nitrogen fixation‐related genes based on Paenibacillus comparative genomics. In order to validate this proposal, we investigated BNF regulatory sequences in Paenibacillus riograndensis SBR 5 T genome. We identified GlnR‐binding sites flanking σ A ‐binding sites upstream from BNF ‐related genes. GlnR binding to these sites was demonstrated by surface plasmon resonance spectroscopy. GlnR‐ DNA affinity is greatly enhanced when GlnR is in complex with feedback‐inhibited (glutamine‐occupied) glutamine synthetase ( GS ). GlnR– GS complex formation is also modulated by ATP and AMP . Thereby, gene repression exerted by the GlnR‐ GS complex is coupled with nitrogen (glutamine levels) and energetic status ( ATP and AMP ). Finally, we propose a DNA ‐looping model based on multiple operator sites that represents a strong and strict regulation for these genes.