bluuebunny/crossref_metadata_2025_split huggingface dataset:
Binding of Azole Antibiotics to
Staphylococcus aureus
Flavohemoglobin Increases Intracellular Oxidative Stress
Authors: Nobre Lígia S. , Todorovic Smilja , Tavares Ana Filipa N. , Oldfield Eric , Hildebrandt Peter , Teixeira Miguel , Saraiva Lígia M. 
Published: January 2010

ABSTRACT

In this work, we report that flavohemoglobin contributes to the azole susceptibility of
Staphylococcus aureus
. We first observed that deletion of the flavohemoglobin gene leads to an increase in the viability of imidazole-treated
S. aureus
cells and that reversion to the wild-type phenotype occurs upon expression of flavohemoglobin from a multicopy plasmid. Further spectroscopic analyses showed that miconazole, the most efficient azole antibiotic against
S. aureus
, ligates to heme of both oxidized and reduced flavohemoglobin. The binding of miconazole to oxidized flavohemoglobin, with an association constant of 1.7 × 10
6
M
−1
, typical of a tight, specific binding equilibrium, results in augmentation of the superoxide production by the enzyme. These results are corroborated by
in vivo
studies showing that imidazole-treated
S. aureus
cells expressing flavohemoglobin contain a larger amount of reactive oxygen species. Moreover, it was observed that the survival of miconazole-treated
S. aureus
internalized by murine macrophages is higher for cells lacking flavohemoglobin. Altogether, the present data revealed that in
S. aureus
, flavohemoglobin enhances the antimicrobial activity of imidazoles via an increase of intracellular oxidative stress.
The ArcB Sensor Kinase of
Escherichia coli
Autophosphorylates by an Intramolecular Reaction
Authors: Peña-Sandoval Gabriela R. , Georgellis Dimitris 
Published: January 2010

ABSTRACT
The Arc two-component system, comprising the ArcB sensor kinase and the ArcA response regulator, modulates the expression of numerous genes in response to the respiratory conditions of growth. ArcB is a tripartite histidine kinase whose activity is regulated by the oxidation of two cytosol-located redox-active cysteine residues that participate in intermolecular disulfide bond formation. Here we show that ArcB autophosphorylates through an intramolecular reaction which diverges from the usually envisaged intermolecular autophosphorylation of homodimeric histidine kinases.
Microscopic Cords, a Virulence-Related Characteristic of
Mycobacterium tuberculosis
, Are Also Present in Nonpathogenic Mycobacteria
Authors: Julián Esther , Roldán Mónica , Sánchez-Chardi Alejandro , Astola Oihane , Agustí Gemma , Luquin Marina 
Published: January 2010

ABSTRACT

The aggregation of mycobacterial cells in a definite order, forming microscopic structures that resemble cords, is known as cord formation, or cording, and is considered a virulence factor in the
M
ycobacterium tuberculosis
complex and the species
M
ycobacterium marinum
. In the 1950s, cording was related to a trehalose dimycolate lipid that, consequently, was named the cord factor. However, modern techniques of microbial genetics have revealed that cording can be affected by mutations in genes not directly involved in trehalose dimycolate biosynthesis. Therefore, questions such as “How does mycobacterial cord formation occur?” and “Which molecular factors play a role in cord formation?” remain unanswered. At present, one of the problems in cording studies is the correct interpretation of cording morphology. Using optical microscopy, it is sometimes difficult to distinguish between cording and clumping, which is a general property of mycobacteria due to their hydrophobic surfaces. In this work, we provide a new way to visualize cords in great detail using scanning electron microscopy, and we show the first scanning electron microscopy images of the ultrastructure of mycobacterial cords, making this technique the ideal tool for cording studies. This technique has enabled us to affirm that nonpathogenic mycobacteria also form microscopic cords. Finally, we demonstrate that a strong correlation exists between microscopic cords, rough colonial morphology, and increased persistence of mycobacteria inside macrophages.
The Ribosomal Protein L2 Interacts with the RNA Polymerase α Subunit and Acts as a Transcription Modulator in
Escherichia coli
Authors: Rippa Valentina , Cirulli Claudia , Di Palo Benedetta , Doti Nunzianna , Amoresano Angela , Duilio Angela 
Published: January 2010

ABSTRACT

Identification of interacting proteins in stable complexes is essential to understand the mechanisms that regulate cellular processes at the molecular level. Transcription initiation in prokaryotes requires coordinated protein-protein and protein-DNA interactions that often involve one or more transcription factors in addition to RNA polymerase (RNAP) subunits. The RNAP α subunit (RNAPα) is a key regulatory element in gene transcription and functions through direct interaction with other proteins to control all stages of this process. A clear description of the RNAPα protein partners should greatly increase our understanding of transcription modulation. A functional proteomics approach was employed to investigate protein components that specifically interact with RNAPα. A tagged form of
Escherichia coli
RNAPα was used as bait to determine the molecular partners of this subunit in a whole-cell extract. Among other interacting proteins, 50S ribosomal protein L2 (RPL2) was clearly identified by mass spectrometry. The direct interaction between RNAPα and RPL2 was confirmed both
in vivo
and
in vitro
by performing coimmunoprecipitation and bacterial two-hybrid experiments. The functional role of this interaction was also investigated in the presence of a ribosomal promoter by using a β-galactosidase gene reporter assay. The results clearly demonstrated that RPL2 was able to increase β-galactosidase expression only in the presence of a specific ribosomal promoter, whereas it was inactive when it was assayed with an unrelated promoter. Interestingly, other ribosomal proteins (L1, L3, L20, and L27) did not have any effect on rRNA expression. The findings reported here strongly suggest that in addition to its role in ribosome assembly the highly conserved RPL2 protein plays a specific and direct role in regulation of transcription.
Direct Evidence for Control of the Pheromone-InducibleprgQOperon ofEnterococcus faecalisPlasmid pCF10 by a Countertranscript-Driven Attenuation Mechanism
Authors: Johnson Christopher M. , Manias Dawn A. , Haemig Heather A. H. , Shokeen Sonia , Weaver Keith E. , Henkin Tina M. , Dunny Gary M. 
Published: January 2010

ABSTRACTThe mating response ofEnterococcus faecaliscells carrying the conjugative plasmid pCF10 is controlled by multiple regulatory circuits. Initiation of transcription of theprgQconjugation operon is controlled by the peptide receptor protein PrgX; binding of the pheromone peptide cCF10 to PrgX abolishes PrgX repression, while binding of the inhibitor peptide iCF10 enhances repression. The results of molecular analysis ofprgQtranscripts and genetic studies suggested that the elongation ofprgQtranscripts past a putative terminator (IRS1) may be controlled by the interaction of nascentprgQmRNAs with a small antisense RNA (Anti-Q) encoded withinprgQ. Direct evidence for interaction of these RNAs, as well as the resulting effects on readthrough ofprgQtranscription, has been limited. Here we report the results of experiments that (i) determine the inherent termination properties ofprgQtranscripts in the absence of Anti-Q; (ii) determine the direct effects of the interaction of Anti-Q with nascentprgQtranscripts in the absence of complicating effects of the PrgX protein; and (iii) begin to dissect the structural components involved in these interactions. The results confirm the existence of alternative terminating and antiterminating forms of nascentprgQtranscriptsin vivoand demonstrate that the interaction of Anti-Q with these transcripts leads to termination via inhibition of antiterminator formation.In vitrotranscription assays support the major results of thein vivostudies. The data support a model for Anti-Q function suggested from recent studies of these RNAs and their interactionsin vitro(S. Shokeen, C. M. Johnson, T. J. Greenfield, D. A. Manias, G. M. Dunny, and K. E. Weaver, submitted for publication).
SufU Is an Essential Iron-Sulfur Cluster Scaffold Protein in
Bacillus subtilis
Authors: Albrecht Alexander G. , Netz Daili J. A. , Miethke Marcus , Pierik Antonio J. , Burghaus Olaf , Peuckert Florian , Lill Roland , Marahiel Mohamed A. 
Published: January 2010

ABSTRACT

Bacteria use three distinct systems for iron-sulfur (Fe/S) cluster biogenesis: the ISC, SUF, and NIF machineries. The ISC and SUF systems are widely distributed, and many bacteria possess both of them. In
Escherichia coli
, ISC is the major and constitutive system, whereas SUF is induced under iron starvation and/or oxidative stress. Genomic analysis of the Fe/S cluster biosynthesis genes in
Bacillus subtilis
suggests that this bacterium's genome encodes only a SUF system consisting of a
sufCDSUB
gene cluster and a distant
sufA
gene. Mutant analysis of the putative Fe/S scaffold genes
sufU
and
sufA
revealed that
sufU
is essential for growth under minimal standard conditions, but not
sufA
. The drastic growth retardation of a conditional mutant depleted of SufU was coupled with a severe reduction of aconitase and succinate dehydrogenase activities in total-cell lysates, suggesting a crucial function of SufU in Fe/S protein biogenesis. Recombinant SufU was devoid of Fe/S clusters after aerobic purification. Upon
in vitro
reconstitution, SufU bound an Fe/S cluster with up to ∼1.5 Fe and S per monomer. The assembled Fe/S cluster could be transferred from SufU to the
apo
form of isopropylmalate isomerase Leu1, rapidly forming catalytically active [4Fe-4S]-containing
holo
-enzyme. In contrast to native SufU, its D43A variant carried a Fe/S cluster after aerobic purification, indicating that the cluster is stabilized by this mutation. Further, we show that
apo
-SufU is an activator of the cysteine desulfurase SufS by enhancing its activity about 40-fold
in vitro
. SufS-dependent formation of
holo
-SufU suggests that SufU functions as an Fe/S cluster scaffold protein tightly cooperating with the SufS cysteine desulfurase.
Specificity of the Type II Secretion Systems of Enterotoxigenic
Escherichia coli
and
Vibrio cholerae
for Heat-Labile Enterotoxin and Cholera Toxin
Authors: Mudrak Benjamin , Kuehn Meta J. 
Published: January 2010

ABSTRACT

The Gram-negative type II secretion (T2S) system is a multiprotein complex mediating the release of virulence factors from a number of pathogens. While an understanding of the function of T2S components is emerging, little is known about what identifies substrates for export. To investigate T2S substrate recognition, we compared mutations affecting the secretion of two highly homologous substrates: heat-labile enterotoxin (LT) from enterotoxigenic
Escherichia coli
(ETEC) and cholera toxin (CT) from
Vibrio cholerae
. Each toxin consists of one enzymatic A subunit and a ring of five B subunits mediating the toxin's secretion. Here, we report two mutations in LT's B subunit (LTB) that reduce its secretion from ETEC without global effects on the toxin. The Q3K mutation reduced levels of secreted LT by half, and as with CT (T. D. Connell, D. J. Metzger, M. Wang, M. G. Jobling, and R. K. Holmes, Infect. Immun. 63:4091-4098, 1995), the E11K mutation impaired LT secretion. Results
in vitro
and
in vivo
show that these mutants are not degraded more readily than wild-type LT. The Q3K mutation did not significantly affect CT B subunit (CTB) secretion from
V. cholerae
, and the E11A mutation altered LT and CTB secretion to various extents, indicating that these toxins are identified as secretion substrates in different ways. The levels of mutant LTB expressed in
V. cholerae
were low or undetectable, but each CTB mutant expressed and secreted at wild-type levels in ETEC. Therefore, ETEC's T2S system seems to accommodate mutations in CTB that impair the secretion of LTB. Our results highlight the exquisitely fine-tuned relationship between T2S substrates and their coordinate secretion machineries in different bacterial species.
Paleoproterozoic subduction in northwestern Canada from near-vertical and wide-angle seismic reflection data
Authors: Oueity Jounada , Clowes Ron M. 
Published: January 2010

Near-vertical incidence and refraction – wide-angle reflection seismic data, recorded as part of Lithoprobe studies in the Paleoproterozoic–Archean domains of Canada’s Northwest Territories, show remarkable reflections from within the upper mantle. A parallel pair of reflectors imaged by the near-vertical data can be traced from Moho levels (∼33 km) down to ∼70 km depth. In a previous study, the reflectors were interpreted as the top and bottom of an ∼1.8 Ga subducted oceanic crust beneath the Hottah terrane. Further inboard, where the seismic line changes its direction from east–west to nearly north–south, another pair of reflectors extends subhorizontally for about 100 km at ∼70 km depth before dipping downward. The subhorizontal reflectors were not correlated with the dipping slab; instead they were interpreted as a separate feature. However, they roughly coincide with a horizontal interface modeled from wide-angle data by an earlier study. Considering the crooked line acquisition geometry, we re-examined both near-vertical incidence and wide-angle reflection data using 2-dimensional (2-D) and 3-D forward and inverse modeling algorithms. Our results demonstrate that the subhorizontal reflectors are the continuation of the relict subducted slab, which now extends laterally for 300 km. Its base is the source of the wide-angle data. The apparent flattening for the near-vertical data is most likely an artifact of projecting a 3-D geometry onto a 2-D cross section. The shallowly subducted slab probably contributed to the thickening and stabilization of the subcrustal lithosphere below the Wopmay orogen.
The use of instability to train the core musculature
Authors: Behm David G. , Drinkwater Eric J. , Willardson Jeffrey M. , Cowley Patrick M. 
Published: January 2010

Training of the trunk or core muscles for enhanced health, rehabilitation, and athletic performance has received renewed emphasis. Instability resistance exercises have become a popular means of training the core and improving balance. Whether instability resistance training is as, more, or less effective than traditional ground-based resistance training is not fully resolved. The purpose of this review is to address the effectiveness of instability resistance training for athletic, nonathletic, and rehabilitation conditioning. The anatomical core is defined as the axial skeleton and all soft tissues with a proximal attachment on the axial skeleton. Spinal stability is an interaction of passive and active muscle and neural subsystems. Training programs must prepare athletes for a wide variety of postures and external forces, and should include exercises with a destabilizing component. While unstable devices have been shown to be effective in decreasing the incidence of low back pain and increasing the sensory efficiency of soft tissues, they are not recommended as the primary exercises for hypertrophy, absolute strength, or power, especially in trained athletes. For athletes, ground-based free-weight exercises with moderate levels of instability should form the foundation of exercises to train the core musculature. Instability resistance exercises can play an important role in periodization and rehabilitation, and as alternative exercises for the recreationally active individual with less interest or access to ground-based free-weight exercises. Based on the relatively high proportion of type I fibers, the core musculature might respond well to multiple sets with high repetitions (e.g., >15 per set); however, a particular sport may necessitate fewer repetitions.
Communication between the AAA+ ring and microtubule-binding domain of dyneinThis paper is one of a selection of papers published in this special issue entitled 8th International Conference on AAA Proteins and has undergone the Journal's usual peer review process.
Authors: Carter Andrew P. , Vale Ronald D. 
Published: January 2010

Dyneins are microtubule motors, the core of which consists of a ring of AAA+ domains. ATP-driven conformational changes of the AAA+ ring are used to drive the movement of a mechanical element (termed the linker domain) that provides the motor’s powerstroke and to change the affinity of the motor for microtubules (strong binding during the power stroke and weak binding to allow stepping and recocking of the linker domain). Dynein’s microtubule-binding domain (MTBD) is located at the end of a 10 nm long anti-parallel coiled coil (the stalk) and conformational changes that alter the affinity for microtubules must propagate through this coiled coil. A recent crystal structure of dynein’s MTBD sheds new light on how this long-range communication along a coiled coil might occur.
Leflunomide induces immunosuppression in collagen-induced arthritis rats by upregulating CD4+CD25+regulatory T cells
Authors: Wang Ting-Yu , Li Jun , Li Chang-Yu , Jin Yong , Lü Xiong-Wen , Wang Xiao-Hua , Zhou Qian 
Published: January 2010

This study was to investigate the effect of leflunomide on the immunosuppressive CD4+CD25+regulatory T cells (CD4+CD25+Tregs) in collagen-induced arthritis (CIA) rats. CIA was induced by collagen type II in Wistar rats. Immunofluorescence flow cytometry and RT-PCR were used to determine the proportion of CD4+CD25+Tregs and the expression of Foxp3 mRNA, respectively. Proliferation of T lymphocytes was assayed with MTT reagent, and the level of transforming growth factor β1 (TGF-β1) in the supernatant of concanavalin A (Con A)-induced T lymphocytes was determined by ELISA kit. Our investigations demonstrated that inhibition of arthritis by leflunomide was related to changes in CD4+CD25+Tregs. In addition, A771726, which is the active metabolite of leflunomide, promoted the differentiation of spleen lymphocytes into CD4+CD25+Tregs, increased antiinflammatory cytokine TGF-β1 secretion, and adjusted the activity of Con A-induced lymphocytes in vitro.
Role of glucagon-like peptide-1 analogues on insulin receptor regulation in diabetic rat hearts
Authors: Hantouche Christine M. , Bitar Khalil M. , Nemer Georges M. , Obeid Mounir Y. , Kadi Lina N. , Der-Boghossian Asdghig H. , Bikhazi Anwar B. 
Published: January 2010

This study focused on the regulation and affinity modulation of the insulin receptor of coronary endothelium and cardiomyocytes in nondiabetic and STZ-induced type 1 diabetic rats. Male rats were divided into the following 9 groups: nondiabetic (N), nondiabetic treated with exendin-4 (NE), nondiabetic treated with dipeptidyl peptidase IV (DPP-IV) inhibitor (NDp), diabetic (D), diabetic treated with insulin (DI), diabetic treated with exendin-4 (DE), diabetic co-treated with insulin and exendin-4 (DIE), diabetic treated with DPP-IV inhibitor (DDp), and diabetic co-treated with insulin and DPP-IV inhibitor (DIDp). After the rats were treated for 1 month, a first-order Bessel function was employed to estimate the insulin binding affinity (with time constant τ = 1/k−n) to its receptors on the coronary endothelium and cardiomyocytes using CHAPS-untreated and CHAPS-treated heart perfusion, respectively. The results showed that diabetes (D) decreased the τ value on the coronary endothelium and increased it on cardiomyocytes compared with the nondiabetic group (N). Treatment with insulin and (or) exendin-4, a glucagon-like peptide-1 (GLP-1) analogue, increased τ on the coronary endothelium only. On the coronary endothelium, τ values of DI and DIDp were normalized. Western blots of the insulin receptor showed upregulation in D, downregulation in DI, and normalization in DE and DDp. Immunohistochemistry and RT-PCR findings indicated atrial natriuretic factor (ANF) in all diabetic ventricles, thus ascertaining hypertrophy. Therefore, negative myocardial effects related to the insulin receptor were diminished in diabetic rats treated with DPP-IV inhibitor and, more efficiently, by exendin-4.
The effect of prey availability on metabolism and activity in the tarantulaPhormictopus cancerides
Authors: Philip B. N. , Shillington C. 
Published: January 2010

Spiders typically exhibit very low resting metabolic rates (RMR) and altered feeding behaviors as mechanisms to survive extended periods of limited food availability. We examined the effect of different periods of food deprivation on RMR and foraging activities in the Hispaniolan giant tarantula ( Phormictopus cancerides (Latreille, 1806)) (Araneae: Theraphosidae). Juvenile tarantulas were separated into two feeding groups and fed once either every 5 or 30 days. Monthly feeding trials were preceded by RMR measurements. During feeding trials, we compared differences between the two groups in (i) prey capture frequency, (ii) time to prey capture, (iii) locomotory activity, and (iv) the predator’s prey detection distance. Metabolic rates increased for the well-fed group but remained constant for individuals fed once a month. Time to prey capture decreased for food-limited individuals and the proportion of individuals that ate during each feeding trial was significantly higher in the 30-day group. Conversely, results for locomotory activity and detection distances were inconclusive.
A New Approximation Scheme Combining the Viscosity Method with Extragradient Method for Mixed Equilibrium Problems
Authors: Peng Jian-Wen , Wu Soon-Yi 
Published: January 2010

AbstractWe introduce a new approximation scheme combining the viscosity method with extragradient method for finding a common element of the set of solutions of a mixed equilibrium problem and the set of fixed points of a finite family of nonexpansive mappings and the set of the variational inequality for a monotone, Lipschitz continuous mapping. We obtain a strong convergence theorem for the sequences generated by these processes in Hilbert spaces. Based on this result, we also get some new and interesting results. The results in this paper generalize, extend, and improve some well-known results in the literature.
Fixed Point Theorems in Cone Banach Spaces
Authors: Karapınar Erdal 
Published: January 2010

AbstractIn this manuscript, a class of self-mappings on cone Banach spaces which have at least one fixed point is considered. More precisely, for a closed and convex subset "Equation missing" of a cone Banach space with the norm "Equation missing", if there exist "Equation missing", "Equation missing", "Equation missing" and "Equation missing" satisfies the conditions "Equation missing" and "Equation missing" for all "Equation missing" , then "Equation missing" has at least one Fixed point.
Fixed Point Theorems for Nonlinear Operators with and without Monotonicity in Partially Ordered Banach Spaces
Authors: Ding Hui-Sheng , Liang Jin , Xiao Ti-Jun 
Published: January 2010

AbstractWe establish two fixed point theorems for nonlinear operators on Banach spaces partially ordered by a cone. The first fixed point theorem is concerned with a class of mixed monotone operators. In the second fixed point theorem, the nonlinear operators are neither monotone nor mixed monotone. We also provide an illustrative example for our second result.
1 Enoch—Complementary or Alternative toMosaic Torah?
Authors: Heger Paul 
Published: January 2010

AbstractThe lack of explicit reference to the Sinaitic revelation in 1 Enoch led scholars to posit a dissident group of Enochic Judaism that abandoned the Torah, preferring Enoch’s revelation. However, the absence of Sinai was imperative for upholding 1 Enoch’s fictitious primeval origin, while implicit references to Sinai abound. Moreover, omission is not proof of non-existence, since many “normative” texts do not mention the Mosaic Torah either. The opinion that so-called Enochians fostered natural law against Torah is untenable, because it does not explain the ritual rules acknowledged by all of Israel. Also there is no evidence for either a split in Jewish society by this purported Enochian group or existence of theological disputes.