bluuebunny/crossref_metadata_2025_split huggingface dataset:
ATPase Activity of
Mycobacterium tuberculosis
SecA1 and SecA2 Proteins and Its Importance for SecA2 Function in Macrophages
Authors: Hou Jie M. , D'Lima Nadia G. , Rigel Nathan W. , Gibbons Henry S. , McCann Jessica R. , Braunstein Miriam , Teschke Carolyn M. 
Published: May 2008

ABSTRACT

The Sec-dependent translocation pathway that involves the essential SecA protein and the membrane-bound SecYEG translocon is used to export many proteins across the cytoplasmic membrane. Recently, several pathogenic bacteria, including
Mycobacterium tuberculosis
, were shown to possess two SecA homologs, SecA1 and SecA2. SecA1 is essential for general protein export. SecA2 is specific for a subset of exported proteins and is important for
M. tuberculosis
virulence. The enzymatic activities of two SecA proteins from the same microorganism have not been defined for any bacteria. Here,
M. tuberculosis
SecA1 and SecA2 are shown to bind ATP with high affinity, though the affinity of SecA1 for ATP is weaker than that of SecA2 or
Escherichia coli
SecA. Amino acid substitution of arginine or alanine for the conserved lysine in the Walker A motif of SecA2 eliminated ATP binding. We used the SecA2(K115R) variant to show that ATP binding was necessary for the SecA2 function of promoting intracellular growth of
M. tuberculosis
in macrophages. These results are the first to show the importance of ATPase activity in the function of accessory SecA2 proteins.
Redox-State Dynamics of Ubiquinone-10 Imply Cooperative Regulation of Photosynthetic Membrane Expression in
Rhodospirillum rubrum
Authors: Grammel Hartmut , Ghosh Robin 
Published: May 2008

ABSTRACT

It is now well established that, for photosynthetic bacteria, the aerobic-to-microaerophilic transition activates the membrane-bound sensor kinase RegB, which subsequently phosphorylates the transcriptional activator RegA, thereby inducing elevated levels of intracellular photosynthetic membranes. The mechanism of RegB activation—in particular, the role of ubiquinone-10—is controversial at present. One problem here is that very limited quantitative in vivo data for the response of the ubiquinone redox state to different cultivation conditions exist. Here, we utilize
Rhodospirillum rubrum
to study the correlation of the quinone redox state to the expression level of photosynthetic membranes and determine an effective response function directly. Our results show that changes in the photosynthetic membrane levels between 50 and 95% of that maximally attainable are associated with only a twofold change in the ubiquinol/ubiquinone ratio and are not necessarily proportional to the total levels of either quinone or [NAD
+
+ NADH]. There is no correlation between the redox potentials of the quinone and pyridine nucleotide pools. Hill function analysis of the photosynthetic membrane induction in response to the quinone redox state suggests that the induction process is highly cooperative. Our results are probably generally applicable to quinone redox regulation in bacteria.
Nitric Oxide Stress Induces Different Responses but Mediates Comparable Protein Thiol Protection inBacillus subtilisandStaphylococcus aureus
Authors: Hochgräfe Falko , Wolf Carmen , Fuchs Stephan , Liebeke Manuel , Lalk Michael , Engelmann Susanne , Hecker Michael 
Published: May 2008

ABSTRACTThe nonpathogenicBacillus subtilisand the pathogenStaphylococcus aureusare gram-positive model organisms that have to cope with the radical nitric oxide (NO) generated by nitrite reductases of denitrifying bacteria and by the inducible NO synthases of immune cells of the host, respectively. The response of both microorganisms to NO was analyzed by using a two-dimensional gel approach. Metabolic labeling of the proteins revealed major changes in the synthesis pattern of cytosolic proteins after the addition of the NO donor MAHMA NONOate. WhereasB. subtilisinduced several oxidative stress-responsive regulons controlled by Fur, PerR, OhrR, and Spx, as well as the general stress response controlled by the alternative sigma factor SigB, the more resistantS. aureusshowed an increased synthesis rate of proteins involved in anaerobic metabolism. These data were confirmed by nuclear magnetic resonance analyses indicating that NO causes a drastically higher increase in the formation of lactate and butanediol inS. aureusthan inB. subtilis. Monitoring the intracellular protein thiol state, we observed no increase in reversible or irreversible protein thiol modifications after NO stress in either organism. Obviously, NO itself does not cause general protein thiol oxidations. In contrast, exposure of cells to NO prior to peroxide stress diminished the irreversible thiol oxidation caused by hydrogen peroxide.
A Cellulose Synthase-Like Protein Involved in Hyphal Tip Growth and Morphological Differentiation in
Streptomyces
Authors: Xu Hongbin , Chater Keith F. , Deng Zixin , Tao Meifeng 
Published: May 2008

ABSTRACT

Cellulose synthase and cellulose synthase-like proteins, responsible for synthesizing β-glucan-containing polysaccharides, play a fundamental role in cellular architectures, such as plant cell and tissue morphogenesis, bacterial biofilm formation, and fruiting-body development. However, the roles of the proteins involved in the developmental process are not well understood. Here, we report that a cellulose synthase-like protein (CslA
Sc
) in
Streptomyces
has a function in hyphal tip growth and morphological differentiation. The

cslA
Sc

replacement mutant showed pleiotropic defects, including the severe delay of aerial-hyphal formation and altered cell wall morphology. Calcofluor white fluorescence analysis demonstrated that polysaccharide synthesis at hyphal tips was dependent on CslA
Sc
.

cslA
Sc

was constitutively transcribed, and an enhanced green fluorescent protein-CslA
Sc
fusion protein was mostly located at the hyphal tips. An extract enriched in morphogenetic chaplin proteins promoted formation of aerial hyphae by the mutant. Furthermore, a two-hybrid experiment indicated that the glycosyltransferase domain of CslA
Sc
interacted with the tropomyosin-like polarity-determining DivIVA protein, suggesting that the tip-located DivIVA governed tip recruitment of the CslA
Sc
membrane protein. These results imply that the cellulose synthase-like protein couples extracellular and cytoskeletal components functioning in tip growth and cell development.
Genes and Enzymes of Azetidine-2-Carboxylate Metabolism: Detoxification and Assimilation of an Antibiotic
Authors: Gross Carol , Felsheim Roderick , Wackett Lawrence P. 
Published: May 2008

ABSTRACT

l
-(−)-Azetidine-2-carboxylate (AC) is a toxic, natural product analog of
l
-proline. This study revealed the genes and biochemical strategy employed by
Pseudomonas
sp. strain A2C to detoxify and assimilate AC as its sole nitrogen source. The gene region from
Pseudomona
s sp. strain A2C required for detoxification was cloned into
Escherichia coli
and sequenced. The 7.0-kb region contained eight identifiable genes. Four encoded putative transporters or permeases for γ-amino acids or drugs. Another gene encoded a homolog of 2-haloacid dehalogenase (HAD). The encoded protein, denoted
l
-azetidine-2-carboxylate hydrolase (AC hydrolase), was highly overexpressed by subcloning. The AC hydrolase was shown to catalyze azetidine ring opening with the production of 2-hydroxy-4-aminobutyrate. AC hydrolase was further demonstrated to be a new hydrolytic member of the HAD superfamily by showing loss of activity upon changing aspartate-12, the conserved active site nucleophile in this family, to an alanine residue. The presence of a gene encoding a potential export chaperone protein, CsaA, adjacent to the AC hydrolase gene suggested that AC hydrolase might be found inside the periplasm in the native
Pseudomonas
strain. Periplasmic and cytoplasmic cell fractions from
Pseudomonas
sp. strain A2C were prepared. A higher specific activity for AC hydrolysis was found in the periplasmic fraction. Protein mass spectrometry further identified AC hydrolase and known periplasmic marker proteins in the periplasmic fraction. A model was proposed in which AC is hydrolyzed in the periplasm and the product of that reaction is transported into and further metabolized in the cytoplasm.
Physical activity and breast cancer risk: impact of timing, type and dose of activity and population subgroup effects
Authors: Friedenreich C M , Cust A E 
Published: May 2008

Objective:To review (1) the epidemiological literature on physical activity and the risk of breast cancer, examining the effect of the different parameters of activity and effect modification within different population subgroups; and (2) the biological mechanisms whereby physical activity may influence the risk of breast cancer.Methods:A review of all published literature to September 2007 was conducted using online databases; 34 case-control and 28 cohort studies were included. The impact of the different parameters of physical activity on the association between activity and the risk of breast cancer was examined by considering the type of activity performed, the timing of activity over the life course and the intensity of activity. Effect modification of this association by menopausal status, body mass index (BMI), racial group, family history of breast cancer, hormone receptor status, energy intake and parity were also considered.Results:Evidence for a risk reduction associated with increased physical activity was found in 47 (76%) of 62 studies included in this review with an average risk decrease of 25–30%. A dose-response effect existed in 28 of 33 studies. Stronger decreases in risk were observed for recreational activity, lifetime or later life activity, vigorous activity, among postmenopausal women, women with normal BMI, non-white racial groups, those with hormone receptor negative tumours, women without a family history of breast cancer and parous women.Conclusions:The effect of physical activity on the risk of breast cancer is stronger in specific population subgroups and for certain parameters of activity that need to be further explored in future intervention trials.
Why it is difficult to detect an illegally bowled cricket delivery with either the naked eye or usual two-dimensional video analysis
Authors: Aginsky K D , Noakes T D 
Published: May 2008

ObjectiveIn this study, the influence of various anatomical and biomechanical factors on the ability to detect the magnitude of elbow extension during the cricket bowling action, with either the naked eye or from conventional two-dimensional video footage was evaluated.DesignDescriptive studySettingOne male bowler who had a large ℌcarrying angleℍ was studied by means of a three-dimensional biomechanical analysis using the Vicon MX13 motion analysis system when bowling at match pace. Photographs were taken from various angles during the bowling delivery action to illustrate factors influencing the visual appearance of an illegal delivery.Main outcome measuresThe influence of extension of the elbow joint and the elbow's anatomically fixed position, known as the “carrying angle”, on the visual perception of an illegal (“thrown”) delivery were the main outcome measures.ResultsThe elbow joint rotates about 90° as a result of humeral rotation during the movement of shoulder circumduction produced by the bowler's delivery action. This causes the plane in which the elbow joint moves to change throughout the delivery action. This movement will also vary between bowlers. The movement of elbow planar flexion/extension can be viewed only when the viewer's eyes are at exactly 90u to the plane of elbow joint movement. Thus, a cricket umpire wishing to detect elbow extension during the bowler's delivery action would need continuously to change his viewing position as the bowler's arm moved from the horizontal to the vertical position at ball release. We show that by viewing the action from only one position, the umpire will be confused by the illusion of a “throw” produced by a large “carrying angle” in some bowlers.ConclusionIt is impossible for an umpire conclusively to cite a bowler for an illegal action based only on naked eye observation. To do this the umpire would need to be in at least three different positions throughout a single delivery. Similarly, video footage shot from at least three different angles during the bowler's delivery action would need to be viewed by the match referee. By viewing the delivery from only one position, the visual illusion of a “throw” will be created by the presence of a large “carrying angle”.
What factors are associated with physical activity in older people, assessed objectively by accelerometry?
Authors: Harris T J , Owen C G , Victor C R , Adams R , Cook D G 
Published: May 2008

Objectives:To assess physical activity (PA) levels measured objectively using accelerometers in community-dwelling older people and to examine the associations with health, disability, anthropometric measures and psychosocial factors.Design:Cross-sectional survey.Setting:Single general practice (primary care centre), United Kingdom.Participants:Random selection of 560 community-dwelling older people at least 65 years old, registered with the practice. 43% (238/560) participated.Assessment of risk factors:Participants completed a questionnaire assessing health, disability, psychosocial factors and PA levels; underwent anthropometric assessment; and wore an accelerometer (Actigraph) for 7 days.Main outcome measures:Average daily accelerometer step-counts and time spent in different PA levels. Associations between step-counts and other factors were examined using linear regression.Results:Average daily step-count was 6443 (95% CI 6032 to 6853). Men achieved 754 (84 to 1424) more steps daily than women. Step-count declined steadily with age. Independent predictors of average daily step-count were: age; general health; disability; diabetes; body mass index; exercise self-efficacy; and perceived exercise control. Activities associated independently with higher step-counts included number of long walks and dog-walking. Only 2.5% (6/238) of participants achieved the recommended 150 minutes weekly of at least moderate-intensity activity in ⩾10 minute bouts; 62% (147/238) achieved none.Conclusions:This is the first population-based sample of older people with objective PA and anthropometric measures. PA levels in older people are well below recommended levels, emphasising the need to increase PA in this age group, particularly in those who are overweight/obese or have diabetes. The independent effects of exercise self-efficacy and exercise control on PA levels highlight their role as potential mediators for intervention studies.
Six-minute walk test in children with chronic conditions
Authors: Hassan J , van der Net J , Helders P J M , Prakken B J , Takken T 
Published: May 2008

ObjectivesThe 6-minute walk test (6MWT) is a frequently used indicator of functional exercise capacity. The goals of this study were to compare the 6-minute walk performance of three paediatric patient groups with that of healthy peers, to assess differences between published reference values and to investigate which anthropometric characteristics best predict 6-minute walk performance.Methods47 children with haemophilia (mean (SD) age 12.5 (2.9) years), 44 with juvenile idiopathic arthritis (JIA) (mean age 9.3 (2.2) years) and 22 with spina bifida (SB) (mean age 10.3 (3.1) years) were included. Subjects performed a 6MWT, and the distance walked (6MWD) was compared with published reference values.ResultsThe haemophilia, JIA and SB patients achieved 90%–92%, 72%–75% and 60%–62% of predicted walking distances, respectively. There were significant associations between 6MWD and age, height and weight in the haemophilia group and 6MWD and height in the JIA group. None of the anthropometric variables was significantly related to 6MWD in the SB group. All anthropometric variables were strongly correlated with walking distance–body weight product (6Mwork) in all groups. Height explained 24% (haemophilia) and 11% (JIA) of the variance in 6MWD and 84% (haemophilia), 78% (JIA) and 73% (SB) of the variance in 6Mwork.ConclusionsWalking distances of children with haemophilia, JIA and SB are significantly reduced compared with healthy references. Walking distance–body weight product seems to be a better outcome measure of the 6MWT compared with distance walked alone. Height is the best predictor of 6MWD and 6Mwork.
Synchrotron Radiation Study of the M2MgSi2O7:Eu2+ Persistent Luminescence Materials
Authors: Holsa Jorma P. , Niittykoski Janne , Kirm Marco , Laamanen Taneli , Lastusaari Mika , Novak Pavel , Raud Juri 
Published: May 2008

The synchrotron radiation luminescence and excitation spectra of the Eu2+ doped M2MgSi2O7 (M = Ca, Sr, Ba) materials were investigated at the SUPERLUMI station of HASYLAB at DESY, Germany. The measurement of the band gap (Eg) energy of all three host lattices using the excitation spectra of Eu2+ gave	values around 7 eV. The measured band gap energies were very similar but slightly higher than those calculated with the DFT-methods. The effect of R3+ co-doping was studied at different temperatures between 10 K and room temperature. A	significant increase in the band gap energy was observed with decreasing temperature. In contrast, no noteworthy change in this value was observed as a function of the R3+ co-doping ion.
Long Persistent White Light Emitting Diode
Authors: Jia Dongdong , Girardi Jenna , Greenland Kelly 
Published: May 2008

Long persistent light emitting diode indicators for emergency indication were made by coat long persistent nanophosphors. During light down conversion when electrical power is available, photons were stored in the nanophosphors. When the electrical power is shut off, the persistent afterglow emission from the nanophosphor can extend the indication time for	another 10 hours. White light is produced by using UV LED and	green and blue nanophosphors.
Long Persistent Greenhouse Film
Authors: Jia Dongdong , Hunter David N. , Wilhelm Justin E. 
Published: May 2008

Thin films for greenhouse application were prepared by doping with long persistent blue and red nanophosphors. Ultra violet and green light in the Sun spectrum were converted into blue and red light by using the nanophosphors. A more efficient blue and red light absorption by the chlorophyll in the plants can let the plants to grow faster. The blue and red light stored in	the long persistent nanophosphors can also extend the growth time for the plants in the greenhouse which will increase productivity.
Reversible disruption of BCL6 repression complexes by CD40 signaling in normal and malignant B cells
Authors: Polo Jose M. , Ci Weimin , Licht Jonathan D. , Melnick Ari 
Published: May 2008

AbstractGerminal center (GC) B cells undergo somatic hypermutation, class switch recombination, and rapid clonal expansion to produce high-affinity antibodies. The BCL6 transcriptional repressor facilitates this phenotype because it can repress DNA damage checkpoint genes. GC B and T cells can make transient direct physical contact; T cells were observed to be associated with dead B-cell fragments. We thus hypothesized that one function of CD40 signaling from T cells within this timeframe could be to modulate BCL6 activity. CD40 signaling rapidly disrupts the ability of BCL6 to recruit the SMRT corepressor complex by excluding it from the nucleus, leading to histone acetylation, RNA polymerase II processivity, and activation of BCL6 target genes, such as CD23b, ATR, and TP53. Washout of CD40 to emulate transient T-cell contact permitted BCL6 target gene mRNA levels to return to their repressed levels, demonstrating that this is a reversible process, which could allow centroblasts that pass quality control to either continue proliferation or undergo terminal differentiation. These data suggest that transient CD40 signaling in the GC might allow T cells to weed out heavily damaged centroblasts while at the same time promoting survival of intact B cells, which could undergo differentiation or additional rounds of proliferation.
Syndromic thrombocytopenia and predisposition to acute myelogenous leukemia caused by constitutional microdeletions on chromosome 21q
Authors: Shinawi Marwan , Erez Ayelet , Shardy Deborah L. , Lee Brendan , Naeem Rizwan , Weissenberger George , Chinault A. Craig , Cheung Sau Wai , Plon Sharon E. 
Published: May 2008

Abstract
Several lines of evidence support the presence of dosage-sensitive genes on chromosome 21 that regulate leukemogenesis and hematopoiesis. We report a detailed clinical and molecular characterization of 3 patients with chronic thrombocytopenia caused by distinct constitutional microdeletions involving chromosomal region 21q22.12. The patients exhibited growth restriction, dysmorphic features, and developmental delays. One patient developed acute myelogenous leukemia (AML) at 6 years of age. All 3 deletions included the RUNX1, CLIC6, DSCR, and KCNE1 genes. Our data provide additional support for the role of RUNX1 haploinsufficiency in megakaryopoiesis and predisposition to AML. The leukemic clone had trisomy 21 resulting from duplication of chromosome 21 containing the RUNX1 deletion. This shows that genes other than RUNX1 must also play a role in AML associated with trisomy 21. We recommend that children with syndromic thrombocytopenia have clinical array-comparative genomic hybridization analysis and appropriate cytogenetic studies to facilitate our ability to provide a definitive diagnosis.
Altered thrombus formation in von Willebrand factor–deficient mice expressing von Willebrand factor variants with defective binding to collagen or GPIIbIIIa
Authors: Marx Isabelle , Christophe Olivier D. , Lenting Peter J. , Rupin Alain , Vallez Marie-Odile , Verbeuren Tony J. , Denis Cécile V. 
Published: May 2008

AbstractThe role of von Willebrand factor (VWF) in thrombosis involves its binding to a number of ligands. To investigate the relative importance of these particular interactions in the thrombosis process, we have introduced mutations into murine VWF (mVWF) cDNA inhibiting VWF binding to glycoprotein (Gp) Ib, GPIIbIIIa, or to fibrillar collagen. These VWF mutants were expressed in VWF-deficient mice (VWF−/−) by using an hydrodynamic injection approach, and the mice were studied in the ferric chloride–induced injury model. Expression of the collagen and the GPIIbIIIa VWF-binding mutants in VWF−/− mice resulted in delayed thrombus growth and significantly increased vessel occlusion times compared with mice expressing wild-type (WT) mVWF (30 ± 3 minutes and 38 ± 4 minutes for the collagen and GPIIbIIIa mutants, respectively, vs 19 ± 3 minutes for WT mVWF). Interestingly, these mutants were able to correct bleeding time as efficiently as WT mVWF. In contrast, VWF−/− mice expressing the GPIb binding mutant failed to restore thrombus formation and were bleeding for as long as they were observed, confirming the critical importance of the VWF-GPIb interaction. Our observations suggest that targeting the VWF-collagen or VWF-GPIIbIIIa interactions could be an interesting alternative for new antithrombotic strategies.