Signal transduction protein PII from Synechococcus elongatus PCC 7942 senses low adenylate energy charge in vitro.

Oleksandra Fokina , Christina Herrmann , Karl Forchhammer (1)

1 Microbiology/Organismic Interactions

PII proteins belong to a family of highly conserved signal transduction proteins widely spread in bacteria, archaea and plants. They respond to the central metabolites ATP, ADP and 2-oxoglutarate (2-OG) and control enzymes, transcription factors and transport proteins involved in nitrogen metabolism. Here we studied the effect of ADP on in vitro PII signalling properties from the cyanobacterium Synechococcus elongatus, a model for oxygenic phototrophic organisms. Different ADP/ATP ratios strongly affected the properties of PII signalling. Increasing ADP antagonized the binding of 2-oxoglutarate and directly affected the interactions of PII with its target proteins. The resulting PII signalling properties indicate that in mixtures of ADP and ATP, PII trimers are occupied with mixtures of adenylate nucleotides. Binding and kinetic activation of N-acetyl-L-glutamate kinase (NAGK) (the controlling enzyme of arginine biosynthesis) by PII was weakened by ADP, but relief from arginine inhibition remained unaffected. On the other hand, ADP enhanced the binding of PII to PipX, a co-activator of transcription factor NtcA and furthermore, antagonised the inhibitory effect of 2-OG on PII-PipX interaction. These results indicate that S. elongatus PII directly senses the adenylate energy charge, resulting in target-dependent differential modification of the PII signalling properties.

Mots clés: Life Sciences

Oleksandra Fokina, Christina Herrmann, Karl Forchhammer. Signal transduction protein PII from Synechococcus elongatus PCC 7942 senses low adenylate energy charge in vitro.. Biochemical Journal, 2011, 440 (1), pp.147-156. ⟨10.1042/BJ20110536⟩. ⟨hal-00642840⟩