HPr antagonizes the anti-σ ⁷⁰ activity of Rsd in Escherichia coli

Abstract

The bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) is a multicomponent system that participates in a variety of physiological processes in addition to the phosphorylation-coupled transport of numerous sugars. In Escherichia coli and other enteric bacteria, enzyme IIA Glc (EIIA Glc ) is known as the central processing unit of carbon metabolism and plays multiple roles, including regulation of adenylyl cyclase, the fermentation/respiration switch protein FrsA, glycerol kinase, and several non-PTS transporters, whereas the only known regulatory role of the E. coli histidine-containing phosphocarrier protein HPr is in the activation of glycogen phosphorylase. Because HPr is known to be more abundant than EIIA Glc in enteric bacteria, we assumed that there might be more regulatory mechanisms connected with HPr. The ligand fishing experiment in this study identified Rsd, an anti-sigma factor known to complex with σ 70 in stationary-phase cells, as an HPr-binding protein in E. coli. Only the dephosphorylated form of HPr formed a tight complex with Rsd and thereby inhibited complex formation between Rsd and σ 70. Dephosphorylated HPr, but not phosphorylated HPr, antagonized the inhibitory effect of Rsd on σ 70-dependent transcriptions both in vivo and in vitro, and also influenced the competition between σ 70 and σ S for core RNA polymerase in the presence of Rsd. Based on these data, we propose that the anti-σ 70 activity of Rsd is regulated by the phosphorylation state-dependent interaction of HPr with Rsd.glucose signaling | sigma factor competition | transcriptional regulation B y monitoring their environment, bacteria ensure the most appropriate response for each environment. One of the sensory systems for monitoring changes in nutrient availability is the phosphoenolpyruvate (PEP):sugar phosphotransferase system (PTS). The PTS is a multicomponent system that catalyzes the concomitant phosphorylation and translocation of numerous sugar substrates across the cytoplasmic membrane. This system consists of two general components, enzyme I (EI) and the histidine-containing phosphocarrier protein HPr, which are common to all PTS sugars, along with many sugar-specific components collectively known as enzyme IIs (EIIs) (1, 2).Each EII complex generally consists of three domains: one integral membrane domain forming the sugar translocation channel (EIIC) and two cytosolic domains (EIIA and EIIB). EI transfers a phosphoryl group from PEP to HPr, and HPr then transfers the phosphoryl group to the different EIIs. Each EII complex forms a cascade of phosphorylated intermediates, and in the presence of a PTS sugar, the EIIA and EIIB domains sequentially transfer the phosphate group from HPr to the incoming sugar. Thus, the phosphorylation states of the PTS components change depending on the availability of a PTS sugar substrate (3, 4).In addition to sugar uptake, the PTS plays an important role as a sensory transduction system to monitor nutritional changes, and its components are involved in the regula...

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

“…It was proposed that under conditions where the PEP level drops and the PTS proteins are barely phosphorylated, the interaction with HPr will favor the breakdown of glycogen. Recently, HPr from E. coli was also reported to interact with the anti- 70 factor Rsd (31). Only unphosphorylated HPr formed a tight complex with Rsd and thus prevented the inhibitory effect of Rsd on 70 dependent transcription, as was shown in in vivo and in vitro experiments.…”

“…In metabolically active cells, the PEP-topyruvate ratio is low and the PTS proteins are barely phosphorylated at His and Cys residues (30). Very low phosphorylation of the PTS proteins is therefore usually observed in cells efficiently metabolizing PTS sugars, such as glucose (28,31). However, growth on non-PTS sugars can also lower the PEP-to-pyruvate ratio and therefore the phosphorylation state of the PTS proteins (28).…”

GigA and GigB are Master Regulators of Antibiotic Resistance, Stress Responses, and Virulence in Acinetobacter baumannii

“…This model is attractive given a previous report that in E. coli, HPr, the carbohydrate-specific ortholog of NPr, interacts with Rsd, a small protein that binds to and mediates the availability of the primary sigma factor D (43,44). It is conceivable that a similar situation may be occurring in A. baumannii; however, searching the AB5075 genome for proteins containing the Rsd domain did not identify any potential matches (data not shown).…”

The General Stress Response σS Is Regulated by a Partner Switch in the Gram-negative Bacterium Shewanella oneidensis

“…66 is controlled by a canonical RsbVWU-like system, whereas in the case of 70 , the partner-switching mechanism is conserved, but Rsd and HPr, which act as an anti-sigma and an anti-sigma antagonist, respectively, are not RsbVW homologs (50,51). It is thus clear that the partner-switching mechanism is a general pathway to efficiently regulate sigma factors.…”