bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alteration of the Fatty Acid Profile of
Streptomyces coelicolor
by Replacement of the Initiation Enzyme 3-Ketoacyl Acyl Carrier Protein Synthase III (FabH)
Authors: Li Yongli , Florova Galina , Reynolds Kevin A. 
Published: May 2005

ABSTRACT

The first elongation step of fatty acid biosynthesis by a type II dissociated fatty acid synthases is catalyzed by 3-ketoacyl-acyl carrier protein (ACP) synthase III (KASIII, FabH). This enzyme, encoded by the
fabH
gene, catalyzes a decarboxylative condensation between an acyl coenzyme A (CoA) primer and malonyl-ACP. In organisms such as
Escherichia coli
, which generate only straight-chain fatty acids (SCFAs), FabH has a substrate preference for acetyl-CoA. In streptomycetes and other organisms which produce a mixture of both SCFAs and branched-chain fatty acids (BCFAs), FabH has been shown to utilize straight- and branched-chain acyl-CoA substrates. We report herein the generation of a
Streptomyces coelicolor
mutant (YL/ecFabH) in which the chromosomal copy of the
fabH
gene has been replaced and the essential process of fatty acid biosynthesis is initiated by plasmid-based expression of the
E. coli
FabH (bearing only 35% amino acid identity to the
Streptomyces
enzyme). The YL/ecFabH mutant produces predominantly SCFAs (86%). In contrast, BCFAs predominate (∼70%) in both the
S. coelicolor
parental strain and
S. coelicolor
YL/sgFabH (a Δ
fabH
mutant carrying a plasmid expressing the
Streptomyces glaucescens
FabH). These results provide the first unequivocal evidence that the substrate specificity of FabH observed in vitro is a determinant of the fatty acid made in an organism. The YL/ecFabH strain grows significantly slower on both solid and liquid media. The levels of FabH activity in cell extracts of YL/ecFabH were also significantly lower than those in cell extracts of YL/sgFabH, suggesting that a decreased rate of fatty acid synthesis may account for the observed decreased growth rate. The production of low levels of BCFAs in YL/ecFabH suggests either that the
E. coli
FabH is more tolerant of different acyl-CoAs substrates than previously thought or that there is an additional pathway for initiation of BCFA biosynthesis in
Streptomyces coelicolor
.
The ExsA Protein of
Bacillus cereus
Is Required for Assembly of Coat and Exosporium onto the Spore Surface
Authors: Bailey-Smith Karen , Todd Sarah J. , Southworth Thomas W. , Proctor John , Moir Anne 
Published: May 2005

ABSTRACT

The outermost layer of spores of the
Bacillus cereus
family is a loose structure known as the exosporium. Spores of a library of Tn
917
-LTV1 transposon insertion mutants of
B. cereus
ATCC 10876 were partitioned into hexadecane; a less hydrophobic mutant that was isolated contained an insertion in the
exsA
promoter region. ExsA is the equivalent of SafA (YrbA) of
Bacillus subtilis
, which is also implicated in spore coat assembly; the gene organizations around both are identical, and both proteins contain a very conserved N-terminal cortex-binding domain of ca. 50 residues, although the rest of the sequence is much less conserved. In particular, unlike SafA, the ExsA protein contains multiple tandem oligopeptide repeats and is therefore likely to have an extended structure. The
exsA
gene is expressed in the mother cell during sporulation. Spores of an
exsA
mutant are extremely permeable to lysozyme and are blocked in late stages of germination, which require coat-associated functions. Two mutants expressing differently truncated versions of ExsA were constructed, and they showed the same gross defects in the attachment of exosporium and spore coat layers. The protein profile of the residual exosporium harvested from spores of the three mutants—two expressing truncated proteins and the mutant with the original transposon insertion in the promoter region—showed some differences from the wild type and from each other, but the major exosporium glycoproteins were retained. The
exsA
gene is extremely important for the normal assembly and anchoring of both the spore coat and exosporium layers in spores of
B. cereus
.
Structure-Based Site-Directed Mutagenesis of the UDP-MurNAc-Pentapeptide-Binding Cavity of the FemX Alanyl Transferase from
Weissella viridescens
Authors: Maillard Antoine P. , Biarrotte-Sorin Sabrina , Villet Régis , Mesnage Stéphane , Bouhss Ahmed , Sougakoff Wladimir , Mayer Claudine , Arthur Michel 
Published: May 2005

ABSTRACT

Weissella viridescens
FemX (FemX
Wv
) belongs to the Fem family of nonribosomal peptidyl transferases that use aminoacyl-tRNA as the amino acid donor to synthesize the peptide cross-bridge found in the peptidoglycan of many species of pathogenic gram-positive bacteria. We have recently solved the crystal structure of FemX
Wv
in complex with the peptidoglycan precursor UDP-MurNAc-pentapeptide and report here the site-directed mutagenesis of nine residues located in the binding cavity for this substrate. Two substitutions, Lys36Met and Arg211Met, depressed FemX
Wv
transferase activity below detectable levels without affecting protein folding. Analogues of UDP-MurNAc-pentapeptide lacking the phosphate groups or the C-terminal
d
-alanyl residues were not substrates of the enzyme. These results indicate that Lys36 and Arg211 participate in a complex hydrogen bond network that connects the C-terminal
d
-Ala residues to the phosphate groups of UDP-MurNAc-pentapeptide and constrains the substrate in a conformation that is essential for transferase activity.
A Multidomain Fusion Protein inListeria monocytogenesCatalyzes the Two Primary Activities for Glutathione Biosynthesis
Authors: Gopal Shubha , Borovok Ilya , Ofer Amos , Yanku Michaela , Cohen Gerald , Goebel Werner , Kreft Jürgen , Aharonowitz Yair 
Published: May 2005

ABSTRACTGlutathione is the predominant low-molecular-weight peptide thiol present in living organisms and plays a key role in protecting cells against oxygen toxicity. Until now, glutathione synthesis was thought to occur solely through the consecutive action of two physically separate enzymes, γ-glutamylcysteine ligase and glutathione synthetase. In this report we demonstrate thatListeria monocytogenescontains a novel multidomain protein (termed GshF) that carries out complete synthesis of glutathione. Evidence for this comes from experiments which showed that in vitro recombinant GshF directs the formation of glutathione from its constituent amino acids and the in vivo effect of a mutation in GshF that abolishes glutathione synthesis, results in accumulation of the intermediate γ-glutamylcysteine, and causes hypersensitivity to oxidative agents. We identified GshF orthologs, consisting of a γ-glutamylcysteine ligase (GshA) domain fused to an ATP-grasp domain, in 20 gram-positive and gram-negative bacteria. Remarkably, 95% of these bacteria are mammalian pathogens. A plausible origin for GshF-dependent glutathione biosynthesis in these bacteria was the recruitment by a GshA ancestor gene of an ATP-grasp gene and the subsequent spread of the fusion gene between mammalian hosts, most likely by horizontal gene transfer.
Structures of the Iron-Sulfur Flavoproteins fromMethanosarcina thermophilaandArchaeoglobus fulgidus
Authors: Andrade Susana L. A. , Cruz Francisco , Drennan Catherine L. , Ramakrishnan Vijay , Rees Douglas C. , Ferry James G. , Einsle Oliver 
Published: May 2005

ABSTRACTIron-sulfur flavoproteins (ISF) constitute a widespread family of redox-active proteins in anaerobic prokaryotes. Based on sequence homologies, their overall structure is expected to be similar to that of flavodoxins, but in addition to a flavin mononucleotide cofactor they also contain a cubane-type [4Fe:4S] cluster. In order to gain further insight into the function and properties of ISF, the three-dimensional structures of two ISF homologs, one from the thermophilic methanogenMethanosarcina thermophilaand one from the hyperthermophilic sulfate-reducing archaeonArchaeoglobus fulgidus, were determined. The structures indicate that ISF assembles to form a tetramer and that electron transfer between the two types of redox cofactors requires oligomerization to juxtapose the flavin mononucleotide and [4Fe:4S] cluster bound to different subunits. This is only possible between different monomers upon oligomerization. Fundamental differences in the surface properties of the two ISF homologs underscore the diversity encountered within this protein family.
Surface Structure and Nanomechanical Properties of
Shewanella putrefaciens
Bacteria at Two pH values (4 and 10) Determined by Atomic Force Microscopy
Authors: Gaboriaud Fabien , Bailet Sidney , Dague Etienne , Jorand Frédéric 
Published: May 2005

ABSTRACT

The nanomechanical properties of gram-negative bacteria (
Shewanella putrefaciens
) were investigated in situ in aqueous solutions at two pH values, specifically, 4 and 10, by atomic force microscopy (AFM). For both pH values, the approach force curves exhibited subsequent nonlinear and linear regimens that were related to the progressive indentation of the AFM tip in the bacterial cell wall, including a priori polymeric fringe (nonlinear part), while the linear part was ascribed to compression of the plasma membrane. These results indicate the dynamic of surface ultrastructure in response to changes in pH, leading to variations in nanomechanical properties, such as the Young's modulus and the bacterial spring constant.
A Gene Encoding
l
-Methionine γ-Lyase Is Present in
Enterobacteriaceae
Family Genomes: Identification and Characterization of
Citrobacter freundii
l
-Methionine γ-Lyase
Authors: Manukhov Ilya V. , Mamaeva Daria V. , Rastorguev Sergei M. , Faleev Nicolai G. , Morozova Elena A. , Demidkina Tatyana V. , Zavilgelsky Gennadii B. 
Published: May 2005

ABSTRACT

Citrobacter freundii
cells produce
l
-methionine γ-lyase when grown on a medium containing
l
-methionine. The nucleotide sequence of the hybrid plasmid with a
C. freundii
EcoRI insert of about 3.0 kbp contained two open reading frames, consisting of 1,194 nucleotides and 1,296 nucleotides, respectively. The first one (denoted
megL
) encoded
l
-methionine γ-lyase. The enzyme was overexpressed in
Escherichia coli
and purified. The second frame encoded a protein belonging to the family of permeases. Regions of high sequence identity with the 3′-terminal part of the
C. freundii megL
gene located in the same regions of
Salmonella enterica
serovar Typhimurium,
Shigella flexneri
,
E. coli
, and
Citrobacter rodentium
genomes were found.
Quorum Sensing Negatively Controls Type III Secretion Regulon Expression in
Pseudomonas aeruginosa
PAO1
Authors: Bleves Sophie , Soscia Chantal , Nogueira-Orlandi Patricia , Lazdunski Andrée , Filloux Alain 
Published: May 2005

ABSTRACT

A systematic analysis of the type III secretion (T3S) genes of
Pseudomonas aeruginosa
strain PAO1 revealed that they are under quorum-sensing control. This observation was supported by the down-regulation of the T3S regulon in the presence of RhlR-C
4
HSL and the corresponding advanced secretion of ExoS in a
rhlI
mutant.
Evolution of Subspecies of
Francisella tularensis
Authors: Svensson Kerstin , Larsson Pär , Johansson Daniel , Byström Mona , Forsman Mats , Johansson Anders 
Published: May 2005

ABSTRACT

Analysis of unidirectional genomic deletion events and single nucleotide variations suggested that the four subspecies of
Francisella tularensis
have evolved by vertical descent. The analysis indicated an evolutionary scenario where the highly virulent
F. tularensis
subsp.
tularensis
(type A) appeared before the less virulent
F. tularensis
subsp.
holarctica
(type B). Compared to their virulent progenitors, attenuated strains of
F. tularensis
exhibited specific unidirectional gene losses.
Non-malignant consequences of decreasing asbestos exposure in the Brazil chrysotile mines and mills
Authors: Bagatin E , Neder J A , Nery L E , Terra-Filho M , Kavakama J , Castelo A , Capelozzi V , Sette A , Kitamura S , Favero M , Moreira-Filho D C , Tavares R , Peres C , Becklake M R 
Published: May 2005

Aims:To investigate the consequences of improvement in the workplace environment over six decades (1940–96) in asbestos miners and millers from a developing country (Brazil).Methods:A total of 3634 Brazilian workers with at least one year of exposure completed a respiratory symptoms questionnaire, chest radiography, and a spirometric evaluation. The study population was separated into three groups whose working conditions improved over time: group I (1940–66, n = 180), group II (1967–76, n = 1317), and group III (1977–96, n = 2137).Results:Respiratory symptoms were significantly related to spirometric abnormalities, smoking, and latency time. Breathlessness, in particular, was also associated with age, pleural abnormality and increased cumulative exposure to asbestos fibres. The odds ratios (OR) for parenchymal and/or non-malignant pleural disease were significantly lower in groups II and III compared to group I subjects (0.29 (0.12–0.69) and 0.19 (0.08–0.45), respectively), independent of age and smoking status. Similar results were found when groups were compared at equivalent latency times (groups IvII: 30–45 years; groups IIvIII: 20–25 years). Ageing, dyspnoea, past and current smoking, and radiographic abnormalities were associated with ventilatory impairment. Lower spirometric values were found in groups I and II compared to group III: lung function values were also lower in higher quartiles of latency and of cumulative exposure in these subjects.Conclusions:Progressive improvement in occupational hygiene in a developing country is likely to reduce the risk of non-malignant consequences of dust inhalation in asbestos miners and millers.
Atrazine in municipal drinking water and risk of low birth weight, preterm delivery, and small-for-gestational-age status
Authors: Villanueva C M , Durand G , Coutté M-B , Chevrier C , Cordier S 
Published: May 2005

Background:Atrazine is a herbicide used extensively worldwide. Bioassays have shown that it is embryotoxic and embryolethal. Evidence of adverse reproductive outcomes from exposure in the general population is sparse.Aims:To evaluate the association between atrazine levels in municipal drinking water and the following adverse reproductive outcomes: increased risk of preterm delivery, low birth weight (LBW), and small-for-gestational-age (SGA) status.Methods:A total of 3510 births that took place from 1 October 1997, to 30 September 1998 were analysed. Atrazine measurements were available for 2661 samples from water treatment plants over the past decade. A seasonal pattern was identified, with atrazine peaking from May to September. The geometric mean of the atrazine level for this period was calculated for each water distribution unit and merged with the individual data by municipality of residence.Results:Atrazine levels in water were not associated with an increased risk of LBW or SGA status and were slightly associated with prematurity. There was an increased risk of SGA status in cases in which the third trimester overlapped in whole or in part with the May–September period, compared with those in which the third trimester occurred totally from October to April (OR = 1.37, 95% CI 1.04 to 1.81). If the entire third trimester took place from May to September, the OR was 1.54 (95% CI 1.11 to 2.13).Conclusions:Low levels of atrazine, a narrow exposure range, and limitations in the exposure assessment partly explain the lack of associations with atrazine. Findings point to the third trimester of pregnancy as the potential vulnerable period for an increased risk of SGA birth. Exposures other than atrazine and also seasonal factors may explain the increased risk.
Urinary mercury concentrations associated with dental restorations in adult women aged 16–49 years: United States, 1999–2000
Authors: Dye B A , Schober S E , Dillon C F , Jones R L , Fryar C , McDowell M , Sinks T H 
Published: May 2005

Background:Mercury amalgam dental restorations have been used by dentists since the mid 19th century and issues on safety continue to be periodically debated within the scientific and public health communities. Previous studies have reported a positive association between urine mercury levels and the number of dental amalgams, but this relation has never been described in a nationally representative sample in the United States.Aims and Methods:Using household interview, dietary interview, dental examination, and laboratory data from the 1999–2000 National Health and Nutrition Examination Survey (NHANES), the association between mercury concentrations and dental restorations was examined in US women of reproductive age.Results:In women of childbearing age, approximately 13% of all posterior dental surfaces were restored with amalgams and the average urinary mercury level in women was low (1.34 μg/l). It is estimated that an increase of 1.8 μg/l in the log transformed values for mercury in urine would occur for each 10 dental surfaces restored with amalgam.Conclusions:Although the findings do not address the important issues of adverse health effects at low thresholds of mercury exposure, they do provide important reference data that should contribute significantly to the ongoing scientific and public health policy debate on the use of dental amalgams in the USA.
Serum markers of collagen metabolism: construction workers compared to sedentary workers
Authors: Kuiper J I , Verbeek J H A M , Everts V , Straub J P , Frings-Dresen M H W 
Published: May 2005

Background:Evaluation of causal relations between physical load and musculoskeletal disorders is hampered by the lack of knowledge as to the biological relevance of different loading parameters and the large variability between individuals. As indicators of molecular changes in the extracellular matrices of structures of the musculoskeletal system, biomarkers of collagen metabolism may provide important information on biological effects of physical load. The carboxyterminal propeptide of type I collagen (PICP) is a serum marker of synthesis and the carboxyterminal telopeptide region of type I collagen (CTx) reflects degradation of type I collagen.Aims:To explore the feasibility of biomarkers of type I collagen metabolism as measures of the effects of physical load at tissue level.Methods:Serum concentrations of PICP and CTx were assessed in a group of male construction workers involved in heavy manual materials handling (n = 47) and in a group of male sedentary workers (n = 49).Results:Serum concentrations of both PICP and CTx seemed to be related to heavy physical work. The ratio PICP/CTx, illustrative of the effective metabolic changes, did not differ between the two groups.Conclusions:The higher turnover rate but similar effective synthesis may be indicative of an increased type I collagen content in the connective tissues as a result of adaptive remodelling in response to years of exposure to physical load. Further validation of these biomarkers is required with respect to dose-response relations and temporal associations between exposure to back load and biomarker concentrations.
AN EVALUATION OF A CONFIGURABLE VLIW MICROARCHITECTURE FOR EMBEDDED DSP APPLICATIONS
Authors: LIU WANLI , ALBONESI DAVID H. , GOSTOMSKI JOHN , PALUM LLOYD , HINTERBERGER DAVE , WANZENRIED RICK , INDOVINA MARK 
Published: May 2005

The last decade has witnessed a significant increase in processor offerings geared towards embedded DSP applications. Such processors are commonly VLIW architectures with special ISA and/or microarchitecture features for speeding up signal processing functions and customization options to improve cost/performance. The Jazz Programmable System Architecture from Improv Systems is one such processor offering. Jazz employs a VLIW architecture which is well-suited to the characteristics of embedded DSP applications such as voice over packet, media processing, and home connectivity. The microarchitecture incorporates overlaid datapaths, distributed register file and memory systems, code compression, and parallel computation and memory access. Jazz permits design-time configuration in an attempt to bridge the gap between the flexibility of a programmable processor and the cost-benefit of full customization. In this paper, we explore the cost/performance tradeoffs of the Jazz microarchitecture on various embedded multimedia applications using a detailed cycle-level simulator as well as area and power models. Through a comparison of the performance, power, and area of different hardware configurations running these applications, we demonstrate how the configurability of the architecture affords a cost-performance benefit over a fixed microarchitecture. Key features of the microarchitecture are quantitatively evaluated in terms of their influence on performance. The relationship between compiler optimizations and processor performance is also explored.
PHYSIOMIC APPROACH TO BIOMECHANICS OF CORONARY MICROCIRCULATION
Authors: KAJIYA MASAHITO , HIRAMATSU OSAMU , YADA TOYOTAKA , TOYOTA EIJI , KIYOOKA TAKAHIKO , MOHRI SATOSHI , SHIMIZU JUICHIRO , OGASAWARA YASUO , KAJIAYA FUMIHIKO 
Published: May 2005

The recently proposed Physiome is considered as a powerful successor to the Genome. The definition of Physiome is the quantitative description of the physiological dynamics or functions of the intact organism. The physiome includes integration of knowledge through functional modules of hierarchical system elements of biological systems, and modeling. Biomechanics will offer potent tools to promote the Physiome. By using modern microvisualization technology with physiomic model, this manuscript introduces our physiomic approach to coronary microcirculation which supplies oxygen and nutrients to heart muscles; 1. Mechanical interaction between coronary blood flow and cardiac contraction, and 2. Capillary network and its function.