Structural basis for the sequestration of the anti-σ⁷⁰factor Rsd from σ⁷⁰by the histidine-containing phosphocarrier protein HPr

Abstract

Histidine-containing phosphocarrier protein (HPr) is a general component of the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) involved in the phosphorylation-coupled transport of numerous sugars called PTS sugars. HPr mainly exists in a dephosphorylated form in the presence of PTS sugars in the medium, while its phosphorylation increases in the absence of PTS sugars. A recent study revealed that the dephosphorylated form of HPr binds and antagonizes the function of the antisigma factor Rsd. This anti-sigma factor sequesters the housekeeping sigma factor σ(70) to facilitate switching of the sigma subunit on RNA polymerase from σ(70) to the stress-responsive sigma factor σ(S) in stationary-phase cells. In this study, the structure of the complex of Rsd and HPr was determined at 2.1 Å resolution and revealed that the binding site for HPr on the surface of Rsd partly overlaps with that for σ(70). The localization of the phosphorylation site on HPr at the binding interface for Rsd explains why phosphorylation of HPr abolishes its binding to Rsd. The mutation of crucial residues involved in the HPr-Rsd interaction significantly influenced the competition between HPr and σ(70) for binding to Rsd both in vitro and in vivo. The results provide a structural basis for the linkage of global gene regulation to nutrient availability in the external environment.

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).…”

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

“…In a previous study, we showed that HPr, a general component of the sugar PTS, is predominantly dephosphorylated during glucose transport and only dephosphorylated HPr interacts with Rsd to antagonize its activity ( 16 , 21 , 40 ). We therefore expected that the Rsd–SpoT interaction could be affected by the phosphorylation state of HPr, resulting in changes in the intracellular level of (p)ppGpp.…”

“…Thus, the phosphorylation states of the PTS components change depending on the availability of PTS sugar substrates ( 20 ). In this way, the PTS monitors nutritional changes in the environment and plays multiple regulatory roles in various metabolic processes, in addition to sugar transport ( 16 , 21 ).…”

Regulation of σ factors by conserved partner switches controlled by divergent signalling systems

“…In E. coli , σ 70 activity is also modulated by the anti‐σ factor Rsd and the histidine phosphorylatable HPr that acts as an anti‐σ factor antagonist. However, even though the mechanism of sequestration and release of the σ factor is alike that of PSS, the two partners Rsd and HPr are not homologous to typical PSS proteins with HPr playing a primary role in the translocation of several sugars across the membrane (Mitchell et al, ; Yuan et al, ; Hofmann et al, ; Park et al, ).…”