Requirements for the phosphorylation of the Escherichia coli EIIA Ntr protein in vivo

248

221

SUMMARYThe metabolite 2-oxoglutarate (also known as α-ketoglutarate, 2-ketoglutaric acid, or oxoglutaric acid) lies at the intersection between the carbon and nitrogen metabolic pathways. This compound is a key intermediate of one of the most fundamental biochemical pathways in carbon metabolism, the tricarboxylic acid (TCA) cycle. In addition, 2-oxoglutarate also acts as the major carbon skeleton for nitrogen-assimilatory reactions. Experimental data support the conclusion that intracellular levels of 2-oxoglutarate fluctuate according to nitrogen and carbon availability. This review summarizes how nature has capitalized on the ability of 2-oxoglutarate to reflect cellular nutritional status through evolution of a variety of 2-oxoglutarate-sensing regulatory proteins. The number of metabolic pathways known to be regulated by 2-oxoglutarate levels has increased significantly in recent years. The signaling properties of 2-oxoglutarate are highlighted by the fact that this metabolite regulates the synthesis of the well-established master signaling molecule, cyclic AMP (cAMP), inEscherichia coli.

Section: The Regulatory Pts (Pts Ntr )mentioning

confidence: 98%

The Emergence of 2-Oxoglutarate as a Master Regulator Metabolite

Huergo

Dixon

2015

248

221

Section: Nitrogen-phosphotransferase Systemmentioning

confidence: 99%

“…Phosphoryl transfer in the nitrogen-PTS has been shown to proceed in vitro (263) and in vivo (264) from PEP to EI Ntr to NPr to EIIA Ntr , i.e., just like the phosphorelay observed for the sugar-PTS. His73 is the single site phosphorylated in EIIA Ntr in vivo (264). In strong contrast to the sugar-PTS, however, phosphoryl transfer from EIIA Ntr -P to a specific small-molecule target has not been reported so far (248).…”

Section: Nitrogen-phosphotransferase Systemmentioning

confidence: 99%

“…However, phosphoryl transfer in vitro between the first two proteins of the two systems is strictly phosphorelay dependent: EI Ntr -P prefers NPr as an acceptor, and likewise, EI-P has a preference for HPr, and the two pairs have little cross-reactivity (257,263). In vivo, EI and Hpr as such are each separately capable of phosphorylating EIIA Ntr (264).…”

Section: Nitrogen-phosphotransferase Systemmentioning

confidence: 99%

See 1 more Smart Citation

Nitrogen Assimilation in Escherichia coli: Putting Molecular Data into a Systems Perspective

Heeswijk¹,

Westerhoff

Boogerd³

2013

232

246

SUMMARY We present a comprehensive overview of the hierarchical network of intracellular processes revolving around central nitrogen metabolism in Escherichia coli . The hierarchy intertwines transport, metabolism, signaling leading to posttranslational modification, and transcription. The protein components of the network include an ammonium transporter (AmtB), a glutamine transporter (GlnHPQ), two ammonium assimilation pathways (glutamine synthetase [GS]-glutamate synthase [glutamine 2-oxoglutarate amidotransferase {GOGAT}] and glutamate dehydrogenase [GDH]), the two bifunctional enzymes adenylyl transferase/adenylyl-removing enzyme (ATase) and uridylyl transferase/uridylyl-removing enzyme (UTase), the two trimeric signal transduction proteins (GlnB and GlnK), the two-component regulatory system composed of the histidine protein kinase nitrogen regulator II (NRII) and the response nitrogen regulator I (NRI), three global transcriptional regulators called nitrogen assimilation control (Nac) protein, leucine-responsive regulatory protein (Lrp), and cyclic AMP (cAMP) receptor protein (Crp), the glutaminases, and the nitrogen-phosphotransferase system. First, the structural and molecular knowledge on these proteins is reviewed. Thereafter, the activities of the components as they engage together in transport, metabolism, signal transduction, and transcription and their regulation are discussed. Next, old and new molecular data and physiological data are put into a common perspective on integral cellular functioning, especially with the aim of resolving counterintuitive or paradoxical processes featured in nitrogen assimilation. Finally, we articulate what still remains to be discovered and what general lessons can be learned from the vast amounts of data that are available now.

“…Inactivation of the ptsN gene from Klebsiella pneumoniae lowered the expression of several RpoN-controlled transcription units (112) Ntr . Nevertheless, in bacteria also possessing EI, HPr, and sugar-specific EIIB and EIIC components, such as most Enterobacteriaceae, a cross talk between the two types of PTS exists (114,115). The activity of EI Ntr was recently shown to be antagonistically regulated by the metabolic intermediates situated at the intersection between carbon and nitrogen metabolism, namely, ␣-ketoglutarate and glutamine (116).…”

Section: Fig 5 Pts-catalyzed Glucose Uptake and The Eiiamentioning

confidence: 99%

The Bacterial Phosphoenolpyruvate:Carbohydrate Phosphotransferase System: Regulation by Protein Phosphorylation and Phosphorylation-Dependent Protein-Protein Interactions

Deutscher

Aké

Derkaoui

et al. 2014

354

374

SUMMARY The bacterial phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS) carries out both catalytic and regulatory functions. It catalyzes the transport and phosphorylation of a variety of sugars and sugar derivatives but also carries out numerous regulatory functions related to carbon, nitrogen, and phosphate metabolism, to chemotaxis, to potassium transport, and to the virulence of certain pathogens. For these different regulatory processes, the signal is provided by the phosphorylation state of the PTS components, which varies according to the availability of PTS substrates and the metabolic state of the cell. PEP acts as phosphoryl donor for enzyme I (EI), which, together with HPr and one of several EIIA and EIIB pairs, forms a phosphorylation cascade which allows phosphorylation of the cognate carbohydrate bound to the membrane-spanning EIIC. HPr of firmicutes and numerous proteobacteria is also phosphorylated in an ATP-dependent reaction catalyzed by the bifunctional HPr kinase/phosphorylase. PTS-mediated regulatory mechanisms are based either on direct phosphorylation of the target protein or on phosphorylation-dependent interactions. For regulation by PTS-mediated phosphorylation, the target proteins either acquired a PTS domain by fusing it to their N or C termini or integrated a specific, conserved PTS regulation domain (PRD) or, alternatively, developed their own specific sites for PTS-mediated phosphorylation. Protein-protein interactions can occur with either phosphorylated or unphosphorylated PTS components and can either stimulate or inhibit the function of the target proteins. This large variety of signal transduction mechanisms allows the PTS to regulate numerous proteins and to form a vast regulatory network responding to the phosphorylation state of various PTS components.