The Synechococcus elongatus P signal transduction protein controls arginine synthesis by complex formation with N-acetyl-L-glutamate kinase.
This communication identifies, for the first time, a receptor protein for signal perception from the P(II) signal transduction protein in the cyanobacterium Synechococcus elongatus. P(II), a phosphoprotein that signals the carbon/nitrogen status of the cells, forms a tight complex with the key enzyme of the arginine biosynthetic pathway, N-acetylglutamate (NAG) kinase. In complex with P(II), the catalytic activity of NAG kinase is strongly enhanced. Complex formation does not require the effector molecules of P(II), 2-oxoglutarate and ATP, but it is highly susceptible to modifications at the phosphorylation site of P(II), Ser-49. Stable complexes were only formed with the non-phosphorylated form of P(II) but not with Ser-49 mutants. In accordance with these data, NAG kinase activity in S. elongatus extracts correlated with the phosphorylation state of P(II), with high NAG kinase activities corresponding to non-phosphorylated P(II) (nitrogen-excess conditions) and low activities to increased levels of P(II) phosphorylation (nitrogen-poor conditions), thus subjecting the key enzyme of arginine biosynthesis to global nitrogen control.
Heinrich
Annette
A
Institut für Mikrobiologie und Molekularbiologie, Interdisziplinäres Forschungszentrum (IFZ), Justus-Liebig Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany.
Maheswaran
Mani
M
Ruppert
Ulrike
U
Forchhammer
Karl
K
D000255:Adenosine Triphosphate / Q000378:metabolism; D001120:Arginine / Q000096:biosynthesis*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D007656:Ketoglutaric Acids / Q000378:metabolism; D046911:Macromolecular Substances; D051922:PII Nitrogen Regulatory Proteins; D010766:Phosphorylation; D017851:Phosphotransferases (Carboxyl Group Acceptor) / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques
D001426:Bacterial Proteins; D007656:Ketoglutaric Acids; D046911:Macromolecular Substances; D051922:PII Nitrogen Regulatory Proteins; D011994:Recombinant Proteins; D012694:Serine; C404143:PIID regulatory protein, Bacteria; D000255:Adenosine Triphosphate; D001120:Arginine; D017851:Phosphotransferases (Carboxyl Group Acceptor); C020650:glutamate 5-kinase