bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propionyl Coenzyme A Is a Common Intermediate in the 1,2-Propanediol and Propionate Catabolic Pathways Needed for Expression of the
prpBCDE
Operon during Growth of
Salmonella enterica
on 1,2-Propanediol
Authors: Palacios Sergio , Starai Vincent J. , Escalante-Semerena Jorge C. 
Published: April 2003

ABSTRACT

The studies reported here identify propionyl coenzyme A (propionyl-CoA) as the common intermediate in the 1,2-propanediol and propionate catabolic pathways of
Salmonella enterica
serovar Typhimurium LT2. Growth on 1,2-propanediol as a carbon and energy source led to the formation and excretion of propionate, whose activation to propionyl-CoA relied on the activities of the propionate kinase (PduW)/phosphotransacetylase (Pta) enzyme system and the CobB sirtuin-controlled acetyl-CoA and propionyl-CoA (Acs, PrpE) synthetases. The different affinities of these systems for propionate ensure sufficient synthesis of propionyl-CoA to support wild-type growth of
S. enterica
under low or high concentrations of propionate in the environment. These redundant systems of propionyl-CoA synthesis are needed because the
prpE
gene encoding the propionyl-CoA synthetase enzyme is part of the
prpBCDE
operon under the control of the PrpR regulatory protein, which needs 2-methylcitrate as a coactivator. Because the synthesis of 2-methylcitrate by PrpC (i.e., the 2-methylcitrate synthase enzyme) requires propionyl-CoA as a substrate, the level of propionyl-CoA needs to be raised by the Acs or PduW-Pta system before 2-methylcitrate can be synthesized and
prpBCDE
transcription can be activated.
The
Bacillus thuringiensis
PlcR-Regulated Gene
inhA2
Is Necessary, but Not Sufficient, for Virulence
Authors: Fedhila Sinda , Gohar Michel , Slamti Leyla , Nel Patricia , Lereclus Didier 
Published: April 2003

ABSTRACT

We previously reported that
Bacillus thuringiensis
strain 407 Cry 32
−
secretes a zinc-requiring metalloprotease, InhA2, that is essential for virulence in orally infected insects. Analysis of the
inhA2
-
lacZ
transcriptional fusion showed that
inhA2
expression is repressed in a PlcR
−
background. Using DNase I footprinting experiments, we demonstrated that PlcR activates
inhA2
transcription directly by binding to a DNA sequence showing a one-residue mismatch with the previously reported PlcR box. It was previously reported that PlcR is essential for
B. thuringiensis
virulence in oral infection by contributing to the synergistic properties of the spores on the insecticidal activity of the Cry1C protein. We used complementation experiments to investigate whether the PlcR
−
phenotype was due to the absence of InhA2. The results indicated that overexpression of
inhA2
in the Δ
plcR
strain did not restore the wild-type phenotype. However, virulence was fully restored in the Δ
inhA2
complemented mutant. Thus,
inhA2
is the first example of a PlcR-regulated gene found to be directly involved in virulence. However, it is not sufficient for pathogenicity when the other members of the PlcR regulon are lacking. This suggests that InhA2 may act in concert with other PlcR-regulated gene products to provide virulence.
Substrate Specificity of the Nonribosomal Peptide Synthetase PvdD fromPseudomonas aeruginosa
Authors: Ackerley David F. , Caradoc-Davies Tom T. , Lamont Iain L. 
Published: April 2003

ABSTRACTPseudomonas aeruginosaPAO1 secretes a siderophore, pyoverdinePAO, which contains a short peptide attached to a dihydroxyquinoline moiety. Synthesis of this peptide is thought to be catalyzed by nonribosomal peptide synthetases, one of which is encoded by thepvdDgene. The first module ofpvdDwas overexpressed inEscherichia coli, and the protein product was purified.l-Threonine, one of the amino acid residues in pyoverdinePAO, was an effective substrate for the recombinant protein in ATP-PPiexchange assays, showing that PvdD has peptide synthetase activity. Other amino acids, includingd-threonine,l-serine, andl-allo-threonine, were not effective substrates, indicating that PvdD has a high degree of substrate specificity. A three-dimensional modeling approach enabled us to identify amino acids that are likely to be critical in determining the substrate specificity of PvdD and to explore the likely basis of the high substrate selectivity. The approach described here may be useful for analysis of other peptide synthetases.
IS
6110
-Mediated Deletion Polymorphism in the Direct Repeat Region of Clinical Isolates of
Mycobacterium tuberculosis
Authors: Sampson S. L. , Warren R. M. , Richardson M. , Victor T. C. , Jordaan A. M. , van der Spuy G. D. , van Helden P. D. 
Published: April 2003

ABSTRACT

This study investigates the phenomenon of IS
6110
-mediated deletion polymorphism in the direct repeat (DR) region of the genome of
Mycobacterium tuberculosis
. Clinical isolates and their putative predecessors were compared using a combination of DR region restriction fragment length polymorphism, IS
6110
DNA fingerprinting, spoligotyping, and DNA sequencing, which allowed the mapping of chromosome structure and deletion junctions. The data suggest that adjacently situated IS
6110
elements mediate genome deletion. However, in contrast to previous reports, deletions appear to be mediated by inversely oriented IS
6110
elements. This suggests that these events may occur via mechanisms other than RecA-mediated homologous recombination. The results underscore the important role of IS
6110
-associated deletion hypervariability in driving
M. tuberculosis
genome evolution.
Agrobacterium tumefaciensVirB6 Protein Participates in Formation of VirB7 and VirB9 Complexes Required for Type IV Secretion
Authors: Jakubowski Simon J. , Krishnamoorthy Vidhya , Christie Peter J. 
Published: April 2003

ABSTRACTThis study characterized the contribution ofAgrobacterium tumefaciensVirB6, a polytopic inner membrane protein, to the formation of outer membrane VirB7 lipoprotein and VirB9 protein multimers required for type IV secretion. VirB7 assembles as a disulfide cross-linked homodimer that associates with the T pilus and a VirB7-VirB9 heterodimer that stabilizes other VirB proteins during biogenesis of the secretion machine. Two presumptive VirB protein complexes, composed of VirB6, VirB7, and VirB9 and of VirB7, VirB9, and VirB10, were isolated by immunoprecipitation or glutathioneS-transferase pulldown assays from detergent-solubilized membrane extracts of wild-type A348 and a strain producing only VirB6 through VirB10 among the VirB proteins. To examine the biological importance of VirB6 complex formation for type IV secretion, we monitored the effects of nonstoichiometric VirB6 production and the synthesis of VirB6 derivatives with 4-residue insertions (VirB6.i4) on VirB7 and VirB9 multimerization, T-pilus assembly, and substrate transfer. AvirB6gene deletion mutant accumulated VirB7 dimers at diminished steady-state levels, whereas complementation with a plasmid bearing wild-typevirB6partially restored accumulation of the dimers. VirB6 overproduction was correlated with formation of higher-order VirB9 complexes or aggregates and also blocked substrate transfer without a detectable disruption of T-pilus production; these phenotypes were displayed by cells grown at 28°C, a temperature that favors VirB protein turnover, but not by cells grown at 20°C. Strains producing several VirB6.i4 mutant proteins assembled novel VirB7 and VirB9 complexes detectable by nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and two strains producing the D60.i4 and L191.i4 mutant proteins translocated IncQ plasmid and VirE2 effector protein substrates in the absence of a detectable T pilus. Our findings support a model that VirB6 mediates formation of VirB7 and VirB9 complexes required for biogenesis of the T pilus and the secretion channel.
Atypical 16S rRNA Gene Copies in
Ochrobactrum intermedium
Strains Reveal a Large Genomic Rearrangement by Recombination between
rrn
Copies
Authors: Teyssier Corinne , Marchandin Hélène , Siméon De Buochberg Michèle , Ramuz Michel , Jumas-Bilak Estelle 
Published: April 2003

ABSTRACT

Ochrobactrum intermedium
is an opportunistic human pathogen belonging to the alpha 2 subgroup of proteobacteria. The 16S rDNA sequences of nine
O. intermedium
isolates from a collection of clinical and environmental isolates exhibited a 46-bp insertion at position 187, which was present in only one sequence among the 82 complete or partial 16S rDNA sequences of
Ochrobactrum
spp. available in data banks. Reverse transcription-PCR experiments showed that the 46-bp insertion remained in the 16S rRNA. The inserted sequence folded into a stem-loop structure, which took place in and prolonged helix H184 of the 16S rRNA molecule. Helix H184 has been described as conserved in length among eubacteria, suggesting the idiosyncratic character of the 46-bp insertion. Pulsed-field gel electrophoresis experiments showed that seven of the clinical isolates carrying the 46-bp insertion belonged to the same clone. Insertion and
rrn
copy numbers were determined by hybridization and I-
Ceu
I digestion. In the set of clonal isolates, the loss of two insertion copies revealed the deletion of a large genomic fragment of 150 kb, which included one
rrn
copy; deletion occurred during the in vivo evolution of the clone. Determination of the
rrn
skeleton suggested that the large genomic rearrangement occurred during events involving homologous recombination between
rrn
copies. The loss of insertion copies suggested a phenomenon of concerted evolution among heterogeneous
rrn
copies.
Nitrogen Regulation of the
codBA
(Cytosine Deaminase) Operon from
Escherichia coli
by the Nitrogen Assimilation Control Protein, NAC
Authors: Muse Wilson B. , Rosario Christopher J. , Bender Robert A. 
Published: April 2003

ABSTRACT

Transcription of the cytosine deaminase (
codBA
) operon of
Escherichia coli
is regulated by nitrogen, with about three times more
codBA
expression in cells grown in nitrogen-limiting medium than in nitrogen-excess medium. β-Galactosidase expression from
codBp-lacZ
operon fusions showed that the nitrogen assimilation control protein NAC was necessary for this regulation. In vitro transcription from the
codBA
promoter with purified RNA polymerase was stimulated by the addition of purified NAC, confirming that no other factors are required. Gel mobility shifts and DNase I footprints showed that NAC binds to a site centered at position −59 relative to the start site of transcription and that mutants that cannot bind NAC there cannot activate transcription. When a longer promoter region (positions −120 to +67) was used, a double footprint was seen with a second 26-bp footprint separated from the first by a hypersensitive site. When a shorter fragment was used (positions −83 to +67), only the primary footprint was seen. Nevertheless, both the shorter and longer fragments showed NAC-mediated regulation in vivo. Cytosine deaminase expression in
Klebsiella pneumoniae
was also regulated by nitrogen in a NAC-dependent manner.
K. pneumoniae
differs from
E. coli
in having two cytosine deaminase genes, an intervening open reading frame between the
codB
and
codA
orthologs, and a different response to hypoxanthine which increased
cod
expression in
K. pneumoniae
but decreased it in
E. coli
.
Essentiality of
clpX
, but Not
clpP
,
clpL
,
clpC
, or
clpE
, in
Streptococcus pneumoniae
R6
Authors: Robertson Gregory T. , Ng Wai-Leung , Gilmour Raymond , Winkler Malcolm E. 
Published: April 2003

ABSTRACT

We show by using a regulated promoter that
clpX
of
Streptococcus pneumoniae
R6 is essential, whereas
clpP
,
clpL
,
clpC
, and
clpE
can be disrupted. The essentiality of
clpX
was initially missed because of duplication and rearrangement in the region of the chromosome containing
clpX
. Depletion of ClpX resulted in a rapid loss of viability without overt changes in cell morphology. Essentiality of
clpX
, but not
clpP
, has not been reported previously.
Isolation of a New Hemimethylated DNA Binding Protein Which Regulates
dnaA
Gene Expression
Authors: d'Alençon Emmanuelle , Taghbalout Aziz , Bristow Claire , Kern Renée , Aflalo Revital , Kohiyama Masamichi 
Published: April 2003

ABSTRACT

In this report, we show that
yccV
, a gene of unknown function, encodes a protein having an affinity for a hemimethylated
oriC
DNA and that the protein negatively controls
dnaA
gene expression in vivo.
A Simple, Effective, and Selective Synthesis Route without Template Effect (Part II) for [2 + 2] Difunctional 28-Membered Macrocyclic Ethers Based on Benzoxazine Dimers and Its Inclusion Phenomena with Metal Ions
Authors: Chirachanchai Suwabun , Phongtamrug Suttinun , Laobuthee Apirat 
Published: April 2003

Abstract
A macrocyclic ether produced from benzoxazine dimers and ditosylated diethylene glycols is a model to show that the cyclization occurs when intramolecular hydrogen bond of benzoxazine dimer is eliminated in the strong basic condition via a selective [2 + 2] pathway without metal template effect. Macrocyclic ethers perform inclusion phenomena at host-guest stoichiometric ratios of 1:1, and 2:1 depending on the type of metal ion, as clarified by UV and 1H NMR.
Catalytic and β-Stereoselective Mannosylation of Several Glycosyl Acceptors with Mannosyl 6-Nitro-2-benzothiazoate
Authors: Hashihayata Takashi , Mandai Hiroki , Mukaiyama Teruaki 
Published: April 2003

Abstract
Mannosylation of several glycosyl acceptors with a novel mannosyl donor having the 6-nitro-2-benzothiazoate function at an anomeric position proceeded smoothly in the presence of a catalytic amount of tetrakis(pentafluorophenyl)boric acid [HB(C6F5)4] to afford the corresponding disaccharides in high yields with good to high β-stereoselectivities.
Preparation of Layered Li[Ni1/2Mn1/2]O2 by Ultrasonic Spray Pyrolysis Method
Authors: Park S H , Kang S K , Kang Y C , Lee Y S , Sun Y K 
Published: April 2003

Abstract
Li[Ni1/2Mn1/2]O2 material was synthesized by ultrasonic spray pyrolysis method. Li[Ni1/2Mn1/2]O2 was characterized by means of X-ray diffraction, charge/discharge cycling, and cyclic voltammetry. The discharge capacities of Li/Li[Ni1/2Mn1/2]O2 cell at 30 and 55 °C slowly decreased with cycling and remained at 166 and 175 mAh/g after 50 cycles, which are 99 and 94% of initial capacities, respectively. The cyclic voltammogram studies of the Li[Ni1/2Mn1/2]O2 electrode showed only one redox peak. This phenomenon might be related to the initial activation process and/or stabilization of Li[Ni1/2Mn1/2]O2 electrode.
Effect of arsenite, maternal age, and embryonic sex on spina bifida, exencephaly, and resorption rates in the splotch mouse
Authors: Martin Lisa J. , Machado Antonio F. , Loza M. Angelica , Mao Gloria E. , Lee Grace S. , Hovland David N. , Cantor Rita M. , Collins Michael D. 
Published: April 2003

AbstractBACKGROUNDThis study examines interactions of a mutation inPax3, embryonic sex, advanced maternal age, and arsenite exposure in the splotch (Sp) mouse model, with the aim of describing gene‐environment interactions for neural tube defects and embryonic lethality.METHODSSplotch heterozygous C57BL/6J mice were crossed to produce offspring of three genotypes with a common maternal genotype that were exposed to either sodium arsenite on gestational day (GD) 8.0, or advanced maternal age (dams older than 12 months). Embryos were extracted on GD 12 and genotyped for bothPax3and sex.RESULTSArsenite treatment was a significant contributor to both exencephaly and spina bifida. Advanced maternal age resulted in a high exencephaly rate inSp/Spfemale embryos (but not other genotypes) and a high overall resorption rate. Arsenite treatment and advanced maternal age resulted in elevated sex ratios (male:female) for heterozygous and wild‐type embryos. The sex ratio was highest for wild‐type embryos and was lowered as the number of mutantPax3alleles increased. The sex ratio was not significantly different from 1.0 for splotch homozygotes. Control litters had spina bifida rates that were 95% in homozygous, 6% in heterozygous, and 0% in wild‐type embryos.CONCLUSIONSIf arsenite produces exencephaly by inactivating the Pax3 protein, then the fact that the exencephaly rate was increased inSp/Spembryos with no functional Pax3 indicates that arsenite may either induce this defect through additional pathways, or may alter the response via modifier genes. Genetic and environmental factors contributed to the determination of murine sex ratios, with female embryos being more susceptible to loss. Birth Defects Research (Part A) 67:231–239, 2003. © 2003 Wiley‐Liss, Inc.
Carbon monoxide‐induced axial skeletal dysmorphogenesis in the chick embryo
Authors: Alexander Peter G. , Tuan Rocky S. 
Published: April 2003

AbstractBACKGROUNDCongenital axial skeletal defects affect two to three individuals per 1,000 live births. Without strong evidence for heritability, the cause is assumed to be multi‐factorial. Carbon monoxide (CO), an increasingly prevalent environmental toxicant, is a potential environmental component in the etiology of these defects. The chick embryo is a useful model for the characterization and assessment of the mechanism(s) of action of basic developmental mechanisms.METHODSWe have determined a critical period and dose for CO teratogenicity and established a model of CO‐induced axial skeletal dysmorphogenesis in the chick embryo. The resulting phenotypes reveal a spectrum of axial skeletal defects ranging from minor defects of the vertebral canal and inter–vertebral discs, to thoraco–lumbar scoliosis, to a tailless phenotype reminiscent of caudal dysgenesis syndrome. These axial skeletal defects have been related to earlier developmental defects in somitogenesis, including errors in segmentation and epithelialization and the expression of the somitic epithelialization factor, Paraxis. We have examined patterns of cell death and apoptosis in CO exposed chick embryos to assess the target tissue(s) involved in the teratogenicity of CO.RESULTSWith respect to the embryonic axis, the neural tube was found to be the most sensitive to CO‐induced apoptosis, followed by the somitic mesoderm and Hensen's node.CONCLUSIONSWe hypothesize that the somitic defects and the resulting axial skeletal dysmorphogenesis are caused by disrupted neural tube or ectoderm functions related to somite formation and maintenance. We also hypothesize that CO‐induced dysmorphogenesis at this critical period of somitogenesis is caused by the overabundance of CO acting endogenously as a cellular signal, while coincidentally exerting its influence as a toxicant of oxygen delivery or utilization. Birth Defects Research (Part A) 67:219–230, 2003. Published 2003 Wiley‐Liss, Inc.
Neural and orofacial defects in Folbp1 knockout mice
Authors: Tang Louisa S. , Finnell Richard H. 
Published: April 2003

AbstractBACKGROUNDFolic acid is essential for the development of the nervous system and other associated structures. Mice deficient in the folic acid‐binding protein one (Folbp1) gene display multiple developmental abnormalities, including neural and craniofacial defects. To better understand potential interactions between Folbp1 gene and selected genes involved in neural and craniofacial morphogenesis, we evaluated the expression patterns of a panel of crucial differentiation markers (Pax‐3, En‐2, Hox‐a1, Shh, Bmp‐4, Wnt‐1, and Pax‐1).METHODSFolbp1 mice were supplemented with low dosages of folinic acid to rescue nullizygotes from dying in utero before gestational day 10. The gene marker analyses were carried out by in situ hybridization.RESULTSIn nullizygote embryos with open cranial neural tube defects, the downregulation of Pax‐3 and En‐2 in the impaired midbrain, along with an observed upregulation of the ventralizing marker Shh in the expanded floor plate, suggested an important regulatory interaction among these three genes. Moreover, the nullizygotes also exhibit craniofacial abnormalities, such as cleft lip and palate. Pax‐3 signals in the impaired medial nasal primordia were significantly increased, whereas Pax‐1 showed no expression in the undeveloped lateral nasal processes. Although Shh was downregulated, Bmp‐4 was strongly expressed in the medial and lateral nasal processes, highlighting the antagonistic activities of these molecules.CONCLUSIONSImpairment of Folbp1 gene function adversely impacts the expression of several critical signaling molecules. Mis‐expression of these molecules, perhaps mediated by Shh, may potentially contribute to the observed failure of neural tube closure and the development of craniofacial defects in the mutant mice. Birth Defects Research (Part A) 67:209–218, 2003. © 2003 Wiley‐Liss, Inc.
Time‐varying intercepts and equilibrium analysis: an extension of the dynamic almost ideal demand model
Authors: Deschamps Philippe J. 
Published: April 2003

AbstractDemographic effects and user costs in demand systems have usually been modelled explicitly. A more robust approach is a state space formulation of the demand system, where time‐varying intercepts account for the effects of unobservable variables. The author embeds such a system in a vector autoregressive distributed lag model, with a Bayesian hierarchical prior. The model is estimated by a Markov chain Monte Carlo method on samples involving quarterly US and UK data. In the US case, the results are compared with a previously published cointegration analysis of the same data. Copyright © 2002 John Wiley & Sons, Ltd.
Retesting Fair's (1978) model on infidelity
Authors: Wells Curt 
Published: April 2003

AbstractModern econometrics stresses the diagnostic testing of estimated models as an important part of the model‐building process. In a survey article published in this journal (Pagan and Vella 1989), methods for testing the validity of the assumptions underlying the censored regression of the Tobit model were presented. This paper questions the numerical results presented there. Indeed, my results concerning the tests when applied to Fair's well‐known model for infidelity (1978) are the opposite of those presented in this journal. Copyright © 2003 John Wiley & Sons, Ltd.
Employee “spy” software: Should you use it?
Authors: Barlow Judith , Bean LuAnn , Hott David D. 
Published: April 2003

AbstractCyber loafing costs companies billions of dollars each year. But should you use the latest employee
“spy” software to monitor your firm's computer users? The authors review a popular new
surveillance tool, and discuss both its benefits and possible risks. © 2003 Wiley Periodicals,
Inc.
It's the law: Protecting audit suspects' rights
Authors: Sinason David , Pacini Carl , Hillison William 
Published: April 2003

AbstractInvestigations into employee embezzlement, theft, and money laundering have taken on a new wrinkle: many now
fall under the requirements of the Fair Credit Reporting Act. How does this affect audits and
investigations? © 2003 Wiley Periodicals, Inc.