Novel Insights in Cyanobacterial PII Signalling
|演題||Novel Insights in Cyanobacterial PII Signalling|
|講演者||Prof. Karl Forchhammer (University of Tubingen, Germany)|
PII signal transduction proteins are highly conserved in bacteria, archaea and plants and have key functions in coordination of central metabolism by integrating signals from carbon, nitrogen and energy of the cell. In the cyanobacterium Synechococcus elongatus PCC7942, PII binds ATP and 2-oxoglutarate (2-OG) in a synergistic manner, with the ATP-binding sites also accepting ADP. Depending on its effector molecule binding status, PII (from this cyanobacterium and other oxygenic phototrophs) complexes and regulates the arginine-controlled enzyme of the cyclic ornitine pathway, N-acetyl-L-glutamate kinase (NAGK), to control arginine biosynthesis and the small coactivator protein of NtcA, PipX, to control nitrogen-responsive gene expression. Regulation of NAGK seems to be universal in oxygenic phototrophs. Further insights into the process of PII-NAGK complex formation have bee obtained by a combination of molecular genetic approaches and structural analysis of PII variants.