Genetics and biochemistry of the peptidoglycan-associated proteins b and c of Escherichia coli K12

Verhoef, Cornelis; Lugtenberg, Ben; Boxtel, Ria van; Graaff, Pieter de; Verheij, Hubertus M.

doi:10.1007/bf00271664

Cited by 89 publications

(64 citation statements)

References 52 publications

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“…At this high OmpR ~ P level, OmpR would be expected to exert pleiotropic effects, i.e., regulating genes normally outside of its repertoire. This situation is similar to a previously isolated envZ mutation (envZ473) that exhibited a pleiotropic phenotype and resulted in the OmpR-dependent regulation of genes that were considered to be outside of its normal regulon, including phoA, phoE, lamB and malE (Slauch et al, 1988;Verhoef et al, 1979;Wandersman et al, 1980;Wanner et al, 1979). Since the cytoplasmic domain of EnvZ (EnvZc) is capable of osmosensing (Wang et al, 2012), and pH sensing the trans-membrane domains likely serve to dampen the activity of the cytoplasmic domain.…”

Section: Tm Domains Modulate Envz Activity But Are Not Essentialsupporting

confidence: 77%

Cytoplasmic sensing by the inner membrane histidine kinase EnvZ

Foo

Gao

Zhang

et al. 2015

Progress in Biophysics and Molecular Biology

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Two-component regulatory systems drive signal transduction in bacteria. The simplest of these employs a membrane sensor kinase and a cytoplasmic response regulator. Environmental sensing is typically coupled to gene regulation. The histidine kinase EnvZ and its cognate response regulator OmpR regulate expression of outer membrane proteins (porins) in response to osmotic stress. We used hydrogen:deuterium exchange mass spectrometry to identify conformational changes in the cytoplasmic domain of EnvZ (EnvZc) that were associated with osmosensing. The osmosensor localized to a seventeen amino acid region of the four-helix bundle of the cytoplasmic domain and flanked the His 243 autophosphorylation site. High osmolality increased autophosphorylation of His 243 , suggesting that these two events were linked. The transmembrane domains were not required for osmosensing, but mutants in the transmembrane domains altered EnvZ activity. A photoactivatable fusion protein composed of EnvZc fused to the fluorophore mEos2 (EnvZc-mEos2) was as capable as EnvZc in supporting OmpR-dependent ompF and ompC transcription. Over-expression of EnvZc reduced activity, indicating that the EnvZ/OmpR system is not robust. Our results support a model in which osmolytes stabilize helix one in the four-helix bundle of EnvZ by increased hydrogen bonding of the peptide backbone, increasing autophosphorylation and downstream signaling. The likelihood that additional histidine kinases use similar cytoplasmic sensing mechanisms is discussed.

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Section: Tm Domains Modulate Envz Activity But Are Not Essentialsupporting

confidence: 77%

Cytoplasmic sensing by the inner membrane histidine kinase EnvZ

Foo

Gao

Zhang

et al. 2015

Progress in Biophysics and Molecular Biology

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“…This sharp change of the OmpR-P concentration appears to account well for the expression patterns of ompF and ompC at high and low osmolarity. However, the regulation of ompF and ompC in the cell may be more complex, as there are cross-talks among the His-Asp phosphorelay systems (40), and other genes besides ompF and ompC are known to be regulated by OmpR-P (41)(42)(43).…”

Section: Discussionmentioning

confidence: 99%

EnvZ-OmpR Interaction and Osmoregulation in Escherichia coli

Cai

Inouye

2002

Journal of Biological Chemistry

262

237

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EnvZ, a histidine kinase/phosphatase in Escherichia coli, responds to the osmolarity changes in the medium by regulating the phosphorylation state of the transcription factor OmpR, which controls the expression levels of outer membrane porin proteins OmpF and OmpC. Although both ompR and envZ genes are located on the ompB locus under the control of the ompB promoter and transcribed as a single polycistronic mRNA, the expression of envZ is known to be significantly less than ompR. However, to date no accurate estimation for the amounts of EnvZ and OmpR in the cell has been carried out. Here we examined the levels of EnvZ and OmpR in the wild-type strain MC4100 by quantitative Western blot analysis using anti-OmpR and anti-EnvZc (cytoplasmic domain of EnvZ) antisera. It was observed that during exponential growth in L-broth medium there were ϳ3500 and 100 molecules per cell of OmpR and EnvZ, respectively. The levels of OmpR and EnvZ in MC4100 cells grown in a high osmolarity medium (nutrient broth with 20% sucrose) were about the same as those grown in L-broth, whereas they were 1.7-fold higher than those in a low osmolarity medium (nutrient broth). With His 10 -OmpR, we also determined that the K d value for the EnvZc-OmpR complex formation is 1.20 ؎ 0.17 M. On the basis of these results, the molecular mechanism of osmoregulation of ompF and ompC is discussed.

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“…Mutant strain CEl166, which is deficient in the outer membrane proteins b, c and d, was isolated from strain CEl163 in three steps by selecting clones that were spontaneously resistant towards bacteriophages TuIa, Me-1 and K3 sequentially as described previously [20]. This mutant is sensitive towards bacteriophage U3, indicating that the core structure of the lipopolysaccharide is intact [21].…”

Section: Strains and Growth Conditionsmentioning

confidence: 99%

31P nuclear magnetic resonance and freeze-fracture electron microscopy studies on Escherichia coli. III. The outer membrane

Burnell

Alphen

Verkleij

et al. 1980

Biochimica et Biophysica Acta (BBA) - Biomembranes

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Summary1. The outer membrane of a phospholipase A-deficient mutant of Escherichia coli K12, isolated without the use of EDTA and lysozyme, showed the same freeze-fracture morphology as that seen in cells and remained stable for hours as observed by 31P-NMR.2.31P-NMR spectroscopy of the isolated outer membranes revealed that the lipopolysaccharide exists in the same physical state as in phospholipid-lipopolysaccharide liposomes and is most probably arranged in a bilayer at 37°C. The outer membrane contains most or all of the phospholipids at 37°C, and aii the phospholipids at 20°C, as a bilayer.3. The 31p-NMR spectroscopy of the outer membranes from a mutant strain lacking the major outer membrane proteins b, c and d (60% of the total outer membrane protein) yields virtually the same spectrum as the wild-type outer membranes, although most of the particles and pits which were observed in wild-type outer membranes in freeze-fracture electron microscopy were absent.4. Whereas treatment of wild-type outer membranes with calcium ions has no effect on the 31p-NMR spectrum, treatment with EDTA results in more motion of the lipopolysaccharide.

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Genetics and biochemistry of the peptidoglycan-associated proteins b and c of Escherichia coli K12

Cited by 89 publications

References 52 publications

Cytoplasmic sensing by the inner membrane histidine kinase EnvZ

Cytoplasmic sensing by the inner membrane histidine kinase EnvZ

EnvZ-OmpR Interaction and Osmoregulation in Escherichia coli

31P nuclear magnetic resonance and freeze-fracture electron microscopy studies on Escherichia coli. III. The outer membrane

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