Interactions between the nitrogen signal transduction protein PII and N-acetyl glutamate kinase in organisms that perform oxygenic photosynthesis.
PII, one of the most conserved signal transduction proteins, is believed to be a key player in the coordination of nitrogen assimilation and carbon metabolism in bacteria, archaea, and plants. However, the identity of PII receptors remains elusive, particularly in photosynthetic organisms. Here we used yeast two-hybrid approaches to identify new PII receptors and to explore the extent of conservation of PII signaling mechanisms between eubacteria and photosynthetic eukaryotes. Screening of Synechococcus sp. strain PCC 7942 libraries with PII as bait resulted in identification of N-acetyl glutamate kinase (NAGK), a key enzyme in the biosynthesis of arginine. The integrity of Ser49, a residue conserved in PII proteins from organisms that perform oxygenic photosynthesis, appears to be essential for NAGK binding. The effect of glnB mutations on NAGK activity is consistent with positive regulation of NAGK by PII. Phylogenetic and yeast two-hybrid analyses strongly suggest that there was conservation of the NAGK-PII regulatory interaction in the evolution of cyanobacteria and chloroplasts, providing insight into the function of eukaryotic PII-like proteins.
Burillo
Sergio
S
División de Genética, Universidad de Alicante, E-03080 Alicante, Spain.
Luque
Ignacio
I
Fuentes
Inmaculada
I
Contreras
Asunción
A
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000502:physiology*; D001483:Base Sequence; D017124:Conserved Sequence; D000458:Cyanobacteria / Q000378:metabolism*; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism*; D051922:PII Nitrogen Regulatory Proteins; D017851:Phosphotransferases (Carboxyl Group Acceptor) / Q000502:physiology*; D010788:Photosynthesis; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques
D001426:Bacterial Proteins; D051922:PII Nitrogen Regulatory Proteins; C404143:PIID regulatory protein, Bacteria; D017851:Phosphotransferases (Carboxyl Group Acceptor); C018721:acetylglutamate kinase; D009584:Nitrogen