title: Role of PII proteins in nitrogen fixation control of Herbaspirillum seropedicae strain SmR1.
abstract: BACKGROUND
  The PII protein family comprises homotrimeric proteins which act as transducers of the cellular nitrogen and carbon status in prokaryotes and plants. In Herbaspirillum seropedicae, two PII-like proteins (GlnB and GlnK), encoded by the genes glnB and glnK, were identified. The glnB gene is monocistronic and its expression is constitutive, while glnK is located in the nlmAglnKamtB operon and is expressed under nitrogen-limiting conditions.
  
  
  RESULTS
  In order to determine the involvement of the H. seropedicae glnB and glnK gene products in nitrogen fixation, a series of mutant strains were constructed and characterized. The glnK- mutants were deficient in nitrogen fixation and they were complemented by plasmids expressing the GlnK protein or an N-truncated form of NifA. The nitrogenase post-translational control by ammonium was studied and the results showed that the glnK mutant is partially defective in nitrogenase inactivation upon addition of ammonium while the glnB mutant has a wild-type phenotype.
  
  
  CONCLUSIONS
  Our results indicate that GlnK is mainly responsible for NifA activity regulation and ammonium-dependent post-translational regulation of nitrogenase in H. seropedicae.
authors.affiliation: National Institute of Science and Technology for Biological Nitrogen Fixation, Department of Biochemistry and Molecular Biology, Universidade Federal do Paraná, CP 19046, Curitiba, PR, 81531-980, Brazil.
authors.forename: Lilian
authors.initials: L
authors.lastname: Noindorf
authors.forename: Ana C
authors.initials: AC
authors.lastname: Bonatto
authors.forename: Rose A
authors.initials: RA
authors.lastname: Monteiro
authors.forename: Emanuel M
authors.initials: EM
authors.lastname: Souza
authors.forename: Liu U
authors.initials: LU
authors.lastname: Rigo
authors.forename: Fabio O
authors.initials: FO
authors.lastname: Pedrosa
authors.forename: Maria B R
authors.initials: MB
authors.lastname: Steffens
authors.forename: Leda S
authors.initials: LS
authors.lastname: Chubatsu
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D042803:Herbaspirillum / Q000235:genetics* / Q000378:metabolism*; D016296:Mutagenesis; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation; D051922:PII Nitrogen Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D000644:Quaternary Ammonium Compounds / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D051922:PII Nitrogen Regulatory Proteins; D000644:Quaternary Ammonium Compounds; D009584:Nitrogen