Global carbon/nitrogen control by PII signal transduction in cyanobacteria:: from signals to targets

P-II signal transduction plays a pervasive role in microbial nitrogen control. Different phylogenetic lineages have developed various signal transduction schemes around the highly conserved core of the signalling system, which consists of the P-II proteins. Among all various bacterial PI, signalling systems, the one in cyanobacteria is so far unique: in unicellular strains, the mode of covalent modification is by serine phosphorylation and the interpretation of the cellular nitrogen status occurs by measuring the 2-oxoglutarate levels. Recent advances have been the identification of the phospho-P-II phosphatase, the resolution of the crystal structure of PI, proteins from Synechococcus and Synechocystis strains and the identification of novel functions of P-II regulation in cyanobacteria, which highlight the central role of P-II signalling for the acclimation to changing carbon-nitrogen regimes. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.