A role for the signal transduction protein PII in the control of nitrate/nitrite uptake in a cyanobacterium.
In the cyanobacterium Synechococcus sp. strain PCC 7942, ammonium exerts a rapid and reversible inhibition of the nitrate and nitrite uptake, and the PII protein (GlnB) is differentially phosphorylated depending on the intracellular N/C balance. RNA/DNA hybridizations, as well as nitrate and nitrite uptake experiments, were carried out with the wild-type strain and a PII-null mutant. The transcriptional control by ammonium of the expression of the nir-nrt ABCD-narB operon remained operative in the mutant but, in contrast to the wild-type strain, the mutant took up nitrate and nitrite even in the presence of ammonium. Moreover, the wild-type phenotype was restored by insertion of a copy of the wild-type glnB gene in the genome of the PII-null mutant. These results indicate that the unphosphorylated form of PII is involved in the short-term inhibition by ammonium of the nitrate and nitrite uptake in Synechococcus sp. strain PCC 7942.
Lee
H M
HM
Département de Biochimie et Génétique Moléculaire, Unité de Physiologie Microbienne, Paris, France.
Flores
E
E
Herrero
A
A
Houmard
J
J
Tandeau de Marsac
N
N
D000643:Ammonium Chloride / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000458:Cyanobacteria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D017136:Ion Transport; D009154:Mutation; D009566:Nitrates / Q000378:metabolism*; D009572:Nitrite Reductases / Q000235:genetics; D009573:Nitrites / Q000378:metabolism*; D009876:Operon / Q000235:genetics; D051922:PII Nitrogen Regulatory Proteins; D010766:Phosphorylation; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction / Q000502:physiology*
D001426:Bacterial Proteins; D009566:Nitrates; D009573:Nitrites; D051922:PII Nitrogen Regulatory Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D000643:Ammonium Chloride; C404143:PIID regulatory protein, Bacteria; D009572:Nitrite Reductases