The general PTS component HPr determines the preference for glucose over mannitol

Abstract

Preferential sugar utilization is a widespread phenomenon in biological systems. Glucose is usually the most preferred carbon source in various organisms, especially in bacteria where it is taken up via the phosphoenolpyruvate:sugar phosphotransferase system (PTS). The currently proposed model for glucose preference over non-PTS sugars in enteric bacteria including E. coli is strictly dependent on the phosphorylation state of the glucose-specific PTS component, enzyme IIAGlc (EIIAGlc). However, the mechanism of the preference among PTS sugars is largely unknown in Gram-negative bacteria. Here, we show that glucose preference over another PTS sugar, mannitol, is absolutely dependent on the general PTS component HPr, but not on EIIAGlc, in E. coli. Dephosphorylated HPr accumulates during the transport of glucose and interacts with the mannitol operon regulator, MtlR, to augment its repressor activity. This interaction blocks the inductive effect of mannitol on the mannitol operon expression and results in the inhibition of mannitol utilization.

Rsd balances (p)ppGpp level by stimulating the hydrolase activity of SpoT during carbon source downshift in Escherichia coli

“…To find a new physiological function of Rsd, we conducted a ligand fishing experiment ( 16 , 24 – 26 ) using an N-terminally hexahistidine-tagged Rsd (His-Rsd) as bait. A crude extract of E. coli MG1655 grown to stationary phase was mixed with TALON metal-affinity resin (Takara Bio) in the absence or presence of His-Rsd.…”

“…We have previously shown that the phosphorylation state of HPr is determined by sugars supplemented to the medium ( 16 , 24 ). As shown in Fig.…”

“…As a result, the accumulated (p)ppGpp controls regulatory networks that coordinate resumption of growth ( 45 ). Considering that the phosphorylation state of HPr is determined by the availability of preferred PTS sugars, such as glucose ( 16 , 24 ) ( Fig. 4 A ), it seems reasonable to assume that (p)ppGpp levels need to be reduced before growth can resume during a carbon source downshift, and this explains the requirement of Rsd for the stimulation of SpoT-catalyzed (p)ppGpp hydrolysis.…”

The Nitrogen Regulatory PII Protein (GlnB) and N -Acetylglucosamine 6-Phosphate Epimerase (NanE) Allosterically Activate Glucosamine 6-Phosphate Deaminase (NagB) in Escherichia coli

“…See the text for protein abbreviations. Regulation of the mannitol catabolic regulator, MtlR, has been described (40). NagB synthesis is regulated by NagC.…”

The phosphocarrier protein HPr of the bacterial phosphotransferase system globally regulates energy metabolism by directly interacting with multiple enzymes in Escherichia coli

“…HPr energizes PTS Enzyme II complexes (7)(8)(9)(10) and phosphorylates the E. coli central regulatory protein, IIA Glc (Crr) (10). HPr has also been shown to interact with and regulate the E. coli glycogen phosphorylase (11)(12)(13), and recently, the mannitol utilization regulator MtlR (13). However, interactions of HPr with other cellular constituents for purposes of regulation have not been demonstrated, and thus, HPr is not recognized as a global regulator.…”