%0 Journal Article %A Gerhardt, Edileusa C. M. %A Araújo, Luíza M. %A Ribeiro, Ronny R. %A Chubatsu, Leda S. %A Scarduelli, Marcelo %A Rodrigues, Thiago E. %A Monteiro, Rose A. %A Pedrosa, Fábio O. %A Souza, Emanuel M. %A Huergo, Luciano F. %T Influence of the ADP/ATP ratio, 2-oxoglutarate and divalent ions on Azospirillum brasilense PII protein signalling %D 2012 %J Microbiology, %V 158 %N 6 %P 1656-1663 %@ 1465-2080 %R https://doi.org/10.1099/mic.0.058446-0 %I Microbiology Society, %X Proteins belonging to the PII family coordinate cellular nitrogen metabolism by direct interaction with a variety of enzymes, transcriptional regulators and transporters. The sensing function of PII relies on its ability to bind the nitrogen/carbon signalling molecule 2-oxoglutarate (2-OG). In Proteobacteria, PII is further subject to reversible uridylylation according to the intracellular levels of glutamine, which reflect the cellular nitrogen status. A number of PII proteins have been shown to bind ADP and ATP in a competitive manner, suggesting that PII might act as an energy sensor. Here, we analyse the influence of the ADP/ATP ratio, 2-OG levels and divalent metal ions on in vitro uridylylation of the Azospirillum brasilense PII proteins GlnB and GlnZ, and on interaction with their targets AmtB, DraG and DraT. The results support the notion that the cellular concentration of 2-OG is a key factor governing occupation of the GlnB and GlnZ nucleotide binding sites by ATP or ADP, with high 2-OG levels favouring the occupation of PII by ATP. Both PII uridylylation and interaction with target proteins responded to the ADP/ATP ratio within the expected physiological range, supporting the concept that PII proteins might act as cellular energy sensors. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.058446-0