105,118 research outputs found
A histidine-kinase cheA gene of Pseudomonas pseudoalcaligens KF707 not only has a key role in chemotaxis but also affects biofilm formation and cell metabolism
No full textA histidine-kinase cheA gene in Pseudomonas pseudoalcaligenes KF707 plays a central role in the regulation of metabolic responses as well as in chemotaxis. Non-chemotactic mutants harboring insertions into the cheA gene were screened for their ability to form biofilms in the Calgary biofilm device. Notably, ≥95% decrease in the number of cells attached to the polystyrene surface was observed in cheA mutants compared to the KF707 wild-type biofilm phenotype. The ability to form mature biofilms was restored to wild-type levels, providing functional copies of the KF707 cheA gene to the mutants. In addition, phenotype micro-arrays and proteomic analyses revealed that several basic metabolic activities and a few periplasmic binding proteins of cheA mutant cells differed compared to those of wild-type cells. These results are interpreted as evidence of a strong integration between chemotactic and metabolic pathways in the process of biofilm development by P. pseudoalcaligenes KF707. © 2011 Taylor & Francis
Preformed Soluble Chemoreceptor Trimers That Mimic Cellular Assembly States and Activate CheA Autophosphorylation
No full textBacterial
chemoreceptors associate with the histidine kinase CheA
and coupling protein CheW to form extended membrane arrays that receive
and transduce environmental signals. A receptor trimers-of-dimers resides
at each vertex of the hexagonal protein lattice. CheA is fully activated and regulated when it is integrated
into the receptor assembly. To mimic these states in solution, we
have engineered chemoreceptor cytoplasmic kinase-control modules (KCMs)
based on the <i>Escherichia coli</i> aspartate receptor
Tar that are covalently fused and trimerized by a foldon domain (Tar<sub>FO</sub>). Small-angle X-ray scattering, multi-angle light scattering,
and pulsed-dipolar electron spin resonance spectroscopy
of spin-labeled proteins indicate that the Tar<sub>FO</sub> modules
assemble into homogeneous trimers wherein the protein interaction
regions closely associate
at the end opposite to the foldon domains. The Tar<sub>FO</sub> variants
greatly increase the saturation levels of phosphorylated CheA (CheA-P),
indicating that the association with a trimer of receptor dimers changes
the fraction of active kinase. However, the rate constants for CheA-P
formation with the Tar variants are low compared to those for autophosphorylation
by free CheA, and net phosphotransfer from CheA to CheY does not increase
commensurately with CheA autophosphorylation. Thus, the Tar variants
facilitate slow conversion to an active form of CheA that then undergoes
stable autophosphorylation and is capable of subsequent phosphotransfer
to CheY. Free CheA is largely incapable of phosphorylation but contains
a small active fraction. Addition of Tar<sub>FO</sub> to CheA promotes
a planar conformation of the regulatory domains consistent with array
models for the assembly state of the ternary complex and different
from that observed with a single inhibitory receptor. Introduction
of Tar<sub>FO</sub> into <i>E. coli</i> cells activates
endogenous CheA to produce increased clockwise flagellar rotation,
with the effects increasing in the presence of the chemotaxis methylation
system (CheB/CheR). Overall, the Tar<sub>FO</sub> modules demonstrate
that trimerized signaling tips self-associate, bind CheA and CheW,
and facilitate conversion of CheA to an active conformation
Dynamic domain arrangement of CheA-CheY complex regulates bacterial thermotaxis, as revealed by NMR
No full textBacteria utilize thermotaxis signal transduction proteins, including CheA, and CheY, to switch the direction of the cell movement. However, the thermally responsive machinery enabling warm-seeking behavior has not been identified. Here we examined the effects of temperature on the structure and dynamics of the full-length CheA and CheY complex, by NMR. Our studies revealed that the CheA-CheY complex exists in equilibrium between multiple states, including one state that is preferable for the autophosphorylation of CheA, and another state that is preferable for the phosphotransfer from CheA to CheY. With increasing temperature, the equilibrium shifts toward the latter state. The temperature-dependent population shift of the dynamic domain arrangement of the CheA-CheY complex induced changes in the concentrations of phosphorylated CheY that are comparable to those induced by chemical attractants or repellents. Therefore, the dynamic domain arrangement of the CheA-CheY complex functions as the primary thermally responsive machinery in warm-seeking behavior.Peer reviewe
TFs for genes identified by DNA methylation in “ChEA 2016”.
No full textTFs for genes identified by DNA methylation in “ChEA 2016”.</p
Structural and chemical requirements for histidine phosphorylation by the chemotaxis kinase CheA
No full textThe CheA histidine kinase initiates the signal transduction pathway of bacterial chemotaxis by autophosphorylating a conserved histidine on its phosphotransferase domain (P1). Site-directed mutations of neighboring conserved P1 residues (Glu-67, Lys-48, and His-64) show that a hydrogen-bonding network controls the reactivity of the phospho-accepting His (His-45) in Thermotoga maritima CheA. In particular, the conservative mutation E67Q dramatically reduces phospho-transfer to P1 without significantly affecting the affinity of P1 for the CheA ATP-binding domain. High resolution crystallographic studies revealed that although all mutants disrupt the hydrogen-bonding network to varying degrees, none affect the conformation of His-45. N-15-NMR chemical shift studies instead showed that Glu-67 functions to stabilize the unfavored (NH)-H-delta 1 tautomer of His-45, thereby rendering the N-epsilon 2 imidazole unprotonated and well positioned for accepting the ATP phosphoryl group
A histidine-kinase cheA gene of Pseudomonas pseudoalcaligenes KF707 not only has a key role in chemotaxis but also affects biofilm formation and cell metabolism
No full textLa pubblicazione descrive per la prima volta l'effetto di una delezione sul gene CheA della chemiotassi sulla formazione dei biofilms in P. pseudoalcaligenes KF70
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Pharmacokinetic profiles of the two major active metabolites of metamizole (dipyrone) in cats following three different routes of administration
No full textThis study was performed to determine pharmacokinetic profiles of the two active metabolites of the analgesic drug metamizole (dipyrone, MET), 4-methylaminoantipyrine (MAA), and 4-aminoantipyrine (AA), after intravenous (i.v., intramuscular (i.m.), and oral (p.o.) administration in cats. Six healthy mixed-breed cats were administered MET (25 mg/kg) by i.v., i.m., or p.o. routes in a crossover design. Adverse clinical signs, namely salivation and vomiting, were detected in all groups (i.v. 67%, i.m. 34%, and p.o. 15%). The mean maximal plasma concentration of MAA for i.v., i.m., and p.o. administrations was 148.63 ± 106.64, 18.74 ± 4.97, and 20.59 ± 15.29 Î1⁄4g/ml, respectively, with about 7 hr of half-life in all routes. Among the administration routes, the area under the plasma concentration curve (AUC) value was the lowest after i.m. administration and the AUCEV/i.v. ratio was higher in p.o. than the i.m. administration without statistical significance. The plasma concentration of AA was detectable up to 24 hr, and the mean plasma concentrations were smaller than MAA. The present results suggest that MET is converted into the active metabolites in cats as in humans. Further pharmacodynamics and safety studies should be performed before any clinical use. 2017 John Wiley & Sons Ltd
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
TFs for genes identified by gene expression in “ENCODE and ChEA Consensus TFs from ChIP-X”.
No full textTFs for genes identified by gene expression in “ENCODE and ChEA Consensus TFs from ChIP-X”.</p
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