The PTS(Ntr) system globally regulates ATP-dependent transporters in Rhizobium leguminosarum

• Published in: Molecular microbiology 2012-04, Vol.84 (1), p.117-129
• Main Authors: Prell, J, Mulley, G, Haufe, F, White, J P, Williams, A, Karunakaran, R, Downie, J A, Poole, P S
• Format: Article
• Language: English
• Subjects: ATP-Binding Cassette Transporters - genetics; ATP-Binding Cassette Transporters - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biological Transport; Gene Expression Regulation, Bacterial; Homeostasis; Mutation; Phosphoenolpyruvate Sugar Phosphotransferase System - genetics; Phosphoenolpyruvate Sugar Phosphotransferase System - metabolism; Phosphorylation; Potassium - metabolism; Protein Kinases - metabolism; Rhizobium leguminosarum - genetics; Rhizobium leguminosarum - growth & development; Rhizobium leguminosarum - metabolism; Transcriptional Activation
• ISSN: 1365-2958
• DOI: 10.1111/j.1365-2958.2012.08014.x

Mutation of ptsP encoding EI(Ntr) of the PTS(Ntr) system in Rhizobium leguminosarum strain Rlv3841 caused a pleiotropic phenotype as observed with many bacteria. The mutant formed dry colonies and grew poorly on organic nitrogen or dicarboxylates. Most strikingly the ptsP mutant had low activity of a broad range of ATP-dependent ABC transporters. This lack of activation, which occurred post-translationally, may explain many of the pleiotropic effects. In contrast proton-coupled transport systems were not inhibited in a ptsP mutant. Regulation by PtsP also involves two copies of ptsN that code for EIIA(Ntr) , resulting in a phosphorylation cascade. As in Escherichia coli, the Rlv3841 PTS(Ntr) system also regulates K(+) homeostasis by transcriptional activation of the high-affinity ATP-dependent K(+) transporter KdpABC. This involves direct interaction of a two-component sensor regulator pair KdpDE with unphosphorylated EIIA(Ntr) . Critically, ptsP mutants, which cannot phosphorylate PtsN1 or PtsN2, had a fully activated KdpABC transporter. This is the opposite pattern from that observed with ABC transporters which apparently require phosphorylation of PtsN. These results suggest that ATP-dependent transport might be regulated via PTS(Ntr) responding to the cellular energy charge. ABC transport may be inactivated at low energy charge, conserving ATP for essential processes including K(+) homeostasis.