Journal article

Publication year: 2005

Pages: 1275-1283

Journal: Microbiology

Volume number: 151

ISSN: 1350-0872

eISSN: 1465-2080

Open access status: Bronze

DOI Link: https://doi.org/10.1099/mic.0.27771-0

Publisher: Microbiology Society

Abstract: 
The phosphorylated signal transcluction protein P-parallel to (P-parallel to-P) in the cyanobacterium Synechocystis sp. strain PCC 6803 is dephosphorylated by PphA, a protein phosphatase of the 2C family (PP2C). In this study, the physiological conditions of P-parallel to-P dephosphorylation were investigated with respect to the in vivo specificity of P-parallel to-P towards PphA and the cellular abundance of PphA in cells growing under different nitrogen regimes. Furthermore, the consequences of impaired P-parallel to-P dephosphorylation with respect to short-term inhibition of glutamine synthetase (GS) were studied. With a contribution of approximately 15 % of total Mn2+-dependent p-nitrophenyl phosphate hydrolysis activity, PphA has only a minor impact on the total PP2C activity in Synechocystis extracts. Nevertheless, residual P-parallel to-P dephosphorylation in PphA-deficient cells could only be observed after prolonged incubation in the presence of ammonium. The abundance of PphA correlates with the phosphorylation state of P-parallel to under nitrogen-replete conditions and is specifically enhanced by nitrite. Regulation of pphA expression operates at the post-transcriptional level. In the presence of nitrate/nitrite, PphA is present in molar excess over P-parallel to-P, enabling the cells to rapidly dephosphorylate P-parallel to-P in response to changing environmental conditions. A PphA-deficient mutant is not impaired in short-term inhibition of GS activity following ammonium treatment. Down-regulation of GS occurs by induction of gif genes (encoding GS inactivating factors 7 and 17), which is controlled by NtcA-mediated gene repression. Thus, impaired P-parallel to-P dephosphorylation does not affect ammonium-prompted inactivation of NtcA.

Harvard Citation style: Kloft, N., Rasch, G. and Forchhammer, K. (2005) Protein phosphatase PphA from Synechocystis sp PCC 6803:: the physiological framework of P_II-P dephosphorylation, Microbiology, 151, pp. 1275-1283. https://doi.org/10.1099/mic.0.27771-0

APA Citation style: Kloft, N., Rasch, G., & Forchhammer, K. (2005). Protein phosphatase PphA from Synechocystis sp PCC 6803:: the physiological framework of P_II-P dephosphorylation. Microbiology. 151, 1275-1283. https://doi.org/10.1099/mic.0.27771-0