Functional analysis of the phosphoprotein PII (glnB gene product) in the cyanobacterium Synechococcus sp. strain PCC 7942.
The PII protein (glnB gene product) in the cyanobacterium Synechococcus sp. strain PCC 7942 signals the cellular N status by being phosphorylated or dephosphorylated at a seryl residue. Here we show that the PII-modifying system responds to the activity of ammonium assimilation via the glutamine synthase-glutamate synthase pathway and to the state of CO2 fixation. To identify possible functions of PII in this microorganism, a PII-deficient mutant was created and its general phenotype was characterized. The analysis shows that the PII protein interferes with the regulation of enzymes required for nitrogen assimilation, although ammonium repression is still detectable in the PII-deficient mutant. We suggest that the phosphorylation and dephosphorylation of PII are part of a complex signal transduction network involved in global nitrogen control in cyanobacteria. In this regulatory process, PII might be involved in mediating the tight coordination between carbon and nitrogen assimilation.
Forchhammer
K
K
Département de Biochimie et Génétique Moléculaire, Institut Pasteur, Paris, France.
Tandeau de Marsac
N
N
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001693:Biological Transport, Active; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002874:Chromosome Mapping; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D008744:Methylamines / Q000378:metabolism; D009154:Mutation; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000378:metabolism; D009572:Nitrite Reductases / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D051922:PII Nitrogen Regulatory Proteins; D010641:Phenotype; D010766:Phosphorylation; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
D001426:Bacterial Proteins; D008744:Methylamines; D051922:PII Nitrogen Regulatory Proteins; D002245:Carbon Dioxide; C404143:PIID regulatory protein, Bacteria; D002244:Carbon; C027451:methylamine; D009565:Nitrate Reductases; D009572:Nitrite Reductases; D050901:Nitrate Reductase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen