A protein involved in co-ordinated regulation of inorganic carbon and glucose metabolism in the facultative photoautotrophic cyanobacteriumSynechocystis PCC6803

Abstract

The involvement of a gene of Synechocystis PCC6803, icfG, in the co-ordinated regulation of inorganic carbon and glucose metabolism, was established. The icfG gene codes for a 72 kDa protein, which shows no homology with those registered in data libraries. Expression of icfG required glucose, the actual inducer probably being glucose-6-phosphate, and was independent of light and of the external inorganic carbon concentration. Mutants carrying an inactivated copy of icfG were constructed. Their growth characteristics were identical to those of the wild type under all regimes except in limiting inorganic carbon with glucose being present either before or after the transfer to the limiting conditions. These conditions completely prevented growth, both in the light and in the dark. The inhibition could be relieved by several intermediates of the tricarboxylic acid cycle. Assays of various enzymic activities related to inorganic carbon uptake and to its assimilation via either the Calvin cycle or phosphoenolpyruvate carboxylase did not reveal the level of action of IcfG. Possible models include a blockage of the assimilation of both carbon sources in the absence of IcfG, or the inhibition of Ci incorporation route(s) essential under limiting inorganic carbon conditions, even when glucose is present, and even in the dark.

Evolution of the PPM-family protein phosphatases in Streptomyces: duplication of catalytic domain and lateral recruitment of additional sensory domains

“…The functions of the microbial PPMs that have been characterized include regulation of spore formation, stress response, cell density during stationary phase, carbon and nitrogen assimilation, vegetative growth, development of fruiting bodies and cell segregation (Beuf et al, 1994;Duncan et al, 1995;Gaidenko et al, 2002;Irmler & Forchhammer, 2001;Rajagopal et al, 2003;Shi et al, 1999;Treuner-Lange et al, 2001;Yang et al, 1996). It is notable that most bacterial species containing relatively large numbers of PPMencoding genes, such as Anabaena sp.…”

The Nitrogen-regulated Response Regulator NrrA Controls Cyanophycin Synthesis and Glycogen Catabolism in the Cyanobacterium Synechocystis sp. PCC 6803

“…PCC 6803 genome, suggesting that these genes are direct targets of NrrA in Synechocystis. A putative NrrA-binding site was also identified to be located upstream of the icfG gene cluster, which encodes a glycogen isoamylase (glgX) and IcfG protein phosphatase participating in the regulation of glucose metabolism in Synechocystis (37). Moreover, the predicted NrrA targets in Synechocystis include genes encoding proteases (prp1, prp2, and pfpI) and the enzymes of arginine biosynthesis (argG and argD) ( Table 1).…”

Gene expression under low-oxygen conditions in the cyanobacterium Synechocystis sp. PCC 6803 demonstrates Hik31-dependent and -independent responses

“…The gene icfG (slr1860) encodes a protein, serine/threonine phosphatase, that is vital for growth in the presence of glucose and this gene is upregulated in the wild-type in the presence of glucose, but not in a DHik31 strain (Beuf et al, 1994;Kahlon et al, 2006;Shi et al, 1999). In our experiment, icfG was part of an eight-gene cluster that exhibited low transcript levels in both strains, but was more abundant in the wild-type than the mutant under aerobic conditions.…”