Search results for "Escherichia coli Proteins"
showing 10 items of 121 documents
Folding and stability of the aquaglyceroporin GlpF: Implications for human aqua(glycero)porin diseases
2015
AbstractAquaporins are highly selective polytopic transmembrane channel proteins that facilitate the permeation of water across cellular membranes in a large diversity of organisms. Defects in aquaporin function are associated with common diseases, such as nephrogenic diabetes insipidus, congenital cataract and certain types of cancer. In general, aquaporins have a highly conserved structure; from prokaryotes to humans. The conserved structure, together with structural dynamics and the structural framework for substrate selectivity is discussed. The folding pathway of aquaporins has been a topic of several studies in recent years. These studies revealed that a conserved protein structure ca…
Characterization of the pleiotropic LysR-type transcription regulator LeuO of Escherichia coli
2019
AbstractLeuO is a pleiotropic LysR-type transcriptional regulator (LTTR) and co-regulator of the abundant nucleoid-associated repressor protein H-NS in Gammaproteobacteria. As other LTTRs, LeuO is a tetramer that is formed by dimerization of the N-terminal DNA-binding domain (DBD) and C-terminal effector-binding domain (EBD). To characterize the Escherichia coli LeuO protein, we screened for LeuO mutants that activate the cas (CRISPR-associated/Cascade) promoter more effectively than wild-type LeuO. This yielded nine mutants carrying amino acid substitutions in the dimerization interface of the regulatory EBD, as shown by solving the EBD’s crystal structure. Superimposing of the crystal str…
Topology and accessibility of the transmembrane helices and the sensory site in the bifunctional transporter DcuB of Escherichia coli.
2011
C(4)-Dicarboxylate uptake transporter B (DcuB) of Escherichia coli is a bifunctional transporter that catalyzes fumarate/succinate antiport and serves as a cosensor of the sensor kinase DcuS. Sites and domains of DcuB were analyzed for their topology relative to the cytoplasmic or periplasmic side of the membrane and their accessibility to the water space. For the topology studies, DcuB was fused at 33 sites to the reporter enzymes PhoA and LacZ that are only active when located in the periplasm or the cytoplasm, respectively. The ratios of the PhoA and LacZ activities suggested the presence of 10 or 11 hydrophilic loops, and 11 or 12 α-helical transmembrane domains (TMDs). The central part…
Structural insights into the GTPase domain of Escherichia coli MnmE protein
2007
The Escherichia coli MnmE protein is a 50-kDa multidomain GTPase involved in tRNA modification. Its homologues in eukaryotes are crucial for mitochondrial respiration and, thus, it is thought that the human protein might be involved in mitochondrial diseases. Unlike Ras, MnmE shows a high intrinsic GTPase activity and requires effective GTP hydrolysis, and not simply GTP binding, to be functionally active. The isolated MnmE G-domain (165 residues) conserves the GTPase activity of the entire protein, suggesting that it contains the catalytic residues for GTP hydrolysis. To explore the GTP hydrolysis mechanism of MnmE, we analyzed the effect of low pH on binding and hydrolysis of GTP, as well…
Engineering a 2D protein-DNA crystal.
2005
(Figure Presented) Weaving with DNA: A DNA-binding protein was used to control the structure of a self-assembled 2D crystal. In the absence of protein, four oligonucleotides hybridize to form a Kagome lattice of interwoven double helices with p3 symmetry (see image). Addition of protein RuvA during assembly changes the symmetry and connectivity to give a DNA-protein crystal with an approximately square unit cell. © 2005 Wiley-VCH Verlag GmbH and Co. KGaA.
Transmembrane signaling in the sensor kinase DcuS of Escherichia coli : A long-range piston-type displacement of transmembrane helix 2
2015
The C4-dicarboxylate sensor kinase DcuS is membrane integral because of the transmembrane (TM) helices TM1 and TM2. Fumarate-induced movement of the helices was probed in vivo by Cys accessibility scanning at the membrane-water interfaces after activation of DcuS by fumarate at the periplasmic binding site. TM1 was inserted with amino acid residues 21-41 in the membrane in both the fumarate-activated (ON) and inactive (OFF) states. In contrast, TM2 was inserted with residues 181-201 in the OFF state and residues 185-205 in the ON state. Replacement of Trp 185 by an Arg residue caused displacement of TM2 toward the outside of the membrane and a concomitant induction of the ON state. Results …
C-terminal amino acids are essential for human heat shock protein 70 dimerization
2014
The human inducible heat shock protein 70 (hHsp70), which is involved in several major pathologies, including neurodegenerative disorders and cancer, is a key molecular chaperone and contributes to the proper protein folding and maintenance of a large number of protein structures. Despite its role in disease, the current structural knowledge of hHsp70 is almost exclusively based on its Escherichia coli homolog, DnaK, even though these two proteins only share ~50 % amino acid identity. For the first time, we describe a complete heterologous production and purification strategy that allowed us to obtain a large amount of soluble, full-length, and non-tagged hHsp70. The protein displayed both …
Regulation of tartrate metabolism by TtdR and relation to the DcuS–DcuR-regulated C4-dicarboxylate metabolism of Escherichia coli
2009
Escherichia coli catabolizes l-tartrate under anaerobic conditions to oxaloacetate by the use of l-tartrate/succinate antiporter TtdT and l-tartrate dehydratase TtdAB. Subsequently, l-malate is channelled into fumarate respiration and degraded to succinate by the use of fumarase FumB and fumarate reductase FrdABCD. The genes encoding the latter pathway (dcuB, fumB and frdABCD) are transcriptionally activated by the DcuS–DcuR two-component system. Expression of the l-tartrate-specific ttdABT operon encoding TtdAB and TtdT was stimulated by the LysR-type gene regulator TtdR in the presence of l- and meso-tartrate, and repressed by O2 and nitrate. Anaerobic expression required a functional fn…
Insight into the primary mode of action of TiO2 nanoparticles on Escherichia coli in the dark.
2015
16 pages; International audience; Large-scale production and incorporation of titanium dioxide nanoparticles (NP-TiO2 ) in consumer products leads to their potential release into the environment and raises the question of their toxicity. The bactericidal mechanism of NP-TiO2 under UV light is known to involve oxidative stress due to the generation of reactive oxygen species. In the dark, several studies revealed that NP-TiO2 can exert toxicological effects. However, the mode of action of these nanoparticles is still controversial. In the present study, we used a combination of fluorescent probes to show that NP-TiO2 causes Escherichia coli membrane depolarization and loss of integrity, lead…
The cytoplasmic PASC domain of the sensor kinase DcuS of Escherichia coli : role in signal transduction, dimer formation, and DctA interaction
2013
The cytoplasmic PAS(C) domain of the fumarate responsive sensor kinase DcuS of Escherichia coli links the transmembrane to the kinase domain. PAS(C) is also required for interaction with the transporter DctA serving as a cosensor of DcuS. Earlier studies suggested that PAS(C) functions as a hinge and transmits the signal to the kinase. Reorganizing the PAS(C) dimer interaction and, independently, removal of DctA, converts DcuS to the constitutive ON state (active without fumarate stimulation). ON mutants were categorized with respect to these two biophysical interactions and the functional state of DcuS: type I-ON mutations grossly reorganize the homodimer, and decrease interaction with Dct…