bluuebunny/crossref_metadata_2025_split huggingface dataset:
Levels of the Secreted
Vibrio cholerae
Attachment Factor GbpA Are Modulated by Quorum-Sensing-Induced Proteolysis
Authors: Jude Brooke A. , Martinez Raquel M. , Skorupski Karen , Taylor Ronald K. 
Published: September 2009

ABSTRACT

Vibrio cholerae
is the etiologic agent of cholera in humans. Intestinal colonization occurs in a stepwise fashion, initiating with attachment to the small intestinal epithelium. This attachment is followed by expression of the toxin-coregulated pilus, microcolony formation, and cholera toxin (CT) production. We have recently characterized a secreted attachment factor, GlcNAc binding protein A (GbpA), which functions in attachment to environmental chitin sources as well as to intestinal substrates. Studies have been initiated to define the regulatory network involved in GbpA induction. At low cell density, GbpA was detected in the culture supernatant of all wild-type (WT) strains examined. In contrast, at high cell density, GbpA was undetectable in strains that produce HapR, the central regulator of the cell density-dependent quorum-sensing system of
V. cholerae
. HapR represses the expression of genes encoding regulators involved in
V. cholerae
virulence and activates the expression of genes encoding the secreted proteases HapA and PrtV. We show here that GbpA is degraded by HapA and PrtV in a time-dependent fashion. Consistent with this, Δ
hapA
Δ
prtV
strains attach to chitin beads more efficiently than either the WT or a Δ
hapA
Δ
prtV
Δ
gbpA
strain. These results suggest a model in which GbpA levels fluctuate in concert with the bacterial production of proteases in response to quorum-sensing signals. This could provide a mechanism for GbpA-mediated attachment to, and detachment from, surfaces in response to environmental cues.
The Glycerol-3-Phosphate Permease GlpT Is the Only Fosfomycin Transporter in
Pseudomonas aeruginosa
Authors: Castañeda-García Alfredo , Rodríguez-Rojas Alexandro , Guelfo Javier R. , Blázquez Jesús 
Published: September 2009

ABSTRACT

Fosfomycin is transported into
Escherichia coli
via both glycerol-3-phosphate (GlpT) and a hexose phosphate transporter (UhpT). Consequently, the inactivation of either
glpT
or
uhpT
confers increased fosfomycin resistance in this species. The inactivation of other genes, including
ptsI
and
cyaA
, also confers significant fosfomycin resistance. It has been assumed that identical mechanisms are responsible for fosfomycin transport into
Pseudomonas aeruginosa
cells. The study of an ordered library of insertion mutants in
P. aeruginosa
PA14 demonstrated that only insertions in
glpT
confer significant resistance. To explore the uniqueness of this resistance target in
P. aeruginosa
, the linkage between fosfomycin resistance and the use of glycerol-3-phosphate was tested. Fosfomycin-resistant (Fos-R) mutants were obtained in LB and minimal medium containing glycerol as the sole carbon source at a frequency of 10
−6
. However, no Fos-R mutants grew on plates containing fosfomycin and glycerol-3-phosphate instead of glycerol (mutant frequency, ≤5 × 10
−11
). In addition, 10 out of 10 independent spontaneous Fos-R mutants, obtained on LB-fosfomycin, harbored mutations in
glpT
, and in all cases the sensitivity to fosfomycin was recovered upon complementation with the wild-type
glpT
gene. The analysis of these mutants provides additional insights into the structure-function relationship of glycerol-3-phosphate the transporter in
P. aeruginosa
. Studies with glucose-6-phosphate and different mutant derivatives strongly suggest that
P. aeruginosa
lacks a specific transport system for this sugar. Thus,
glpT
seems to be the only fosfomycin resistance mutational target in
P. aeruginosa
. The high frequency of Fos-R mutations and their apparent lack of fitness cost suggest that Fos-R variants will be obtained easily in vivo upon the fosfomycin treatment of
P. aeruginosa
infections.
Roles of Periplasmic Chaperone Proteins in the Biogenesis of Serine Protease Autotransporters of
Enterobacteriaceae
Authors: Ruiz-Perez Fernando , Henderson Ian R. , Leyton Denisse L. , Rossiter Amanda E. , Zhang Yinghua , Nataro James P. 
Published: September 2009

ABSTRACT

The serine protease autotransporters of
Enterobacteriaceae
(SPATEs) represent a large family of virulence factors. The prevailing model for autotransporter secretion comprises entry to the periplasm via the Sec apparatus, followed by an obscure series of steps in which the C terminus of the periplasmic species inserts into the outer membrane as a β-barrel protein, accompanied by translocation of the passenger domain to the bacterial cell surface. Little is known about the fate of the autotransporter proteins in the periplasm, including whether accessory periplasmic proteins are involved in translocation to the external milieu. Here we studied the role of the major periplasmic chaperones in the biogenesis of EspP, a prototype SPATE protein produced by
Escherichia coli
O157:H7. The yeast two-hybrid approach, secretion analysis of chaperone mutant strains, and surface plasmon resonance analysis (SPR) revealed direct protein-protein interactions between the periplasmic SurA and DegP chaperones and either the EspP-β or EspP passenger domains. The secretion of EspP was moderately reduced in the
surA
and
skp
mutant strains but severely impaired in the
degP
background. Site-directed mutagenesis of highly conserved aromatic amino acid residues in the SPATE family resulted in ∼80% reduction of EspP secretion. Synthetic peptides containing aromatic residues derived from the EspP passenger domain blocked DegP and SurA binding to the passenger domain. SPR suggested direct protein-protein interaction between periplasmic chaperones and the unfolded EspP passenger domain. Our data suggest that translocation of AT proteins may require accessory factors, calling into question the moniker “autotransporter.”
Comparative Structure-Function Analysis of Mannose-Specific FimH Adhesins from
Klebsiella pneumoniae
and
Escherichia coli
Authors: Stahlhut Steen G. , Tchesnokova Veronika , Struve Carsten , Weissman Scott J. , Chattopadhyay Sujay , Yakovenko Olga , Aprikian Pavel , Sokurenko Evgeni V. , Krogfelt Karen Angeliki 
Published: September 2009

ABSTRACT

FimH, the adhesive subunit of type 1 fimbriae expressed by many enterobacteria, mediates mannose-sensitive binding to target host cells. At the same time, fine receptor-structural specificities of FimH from different species can be substantially different, affecting bacterial tissue tropism and, as a result, the role of the particular fimbriae in pathogenesis. In this study, we compared functional properties of the FimH proteins from
Escherichia coli
and
Klebsiella pneumoniae
, which are both 279 amino acids in length but differ by some ∼15% of residues. We show that
K. pneumoniae
FimH is unable to mediate adhesion in a monomannose-specific manner via terminally exposed Manα(1-2) residues in N-linked oligosaccharides, which are the structural basis of the tropism of
E. coli
FimH for uroepithelial cells. However,
K. pneumoniae
FimH can bind to the terminally exposed Manα(1-3)Manβ(1-4)GlcNAcβ1 trisaccharide, though only in a shear-dependent manner, wherein the binding is marginal at low shear force but enhanced sevenfold under increased shear. A single mutation in the
K. pneumoniae
FimH, S62A, converts the mode of binding from shear dependent to shear independent. This mutation has occurred naturally in the course of endemic circulation of a nosocomial uropathogenic clone and is identical to a pathogenicity-adaptive mutation found in highly virulent uropathogenic strains of
E. coli
, in which it also eliminates the dependence of
E. coli
binding on shear. The shear-dependent binding properties of the
K. pneumoniae
and
E. coli
FimH proteins are mediated via an allosteric catch bond mechanism. Thus, despite differences in FimH structure and fine receptor specificity, the shear-dependent nature of FimH-mediated adhesion is highly conserved between bacterial species, supporting its remarkable physiological significance.
Polar Positioning of a Conjugation Protein from the Integrative and Conjugative Element ICEBs1ofBacillus subtilis
Authors: Berkmen Melanie B. , Lee Catherine A. , Loveday Emma-Kate , Grossman Alan D. 
Published: September 2009

ABSTRACTICEBs1is an integrative and conjugative element found in the chromosome ofBacillus subtilis. ICEBs1encodes functions needed for its excision and transfer to recipient cells. We found that the ICEBs1geneconE(formerlyyddE) is required for conjugation and that conjugative transfer of ICEBs1requires a conserved ATPase motif of ConE. ConE belongs to the HerA/FtsK superfamily of ATPases, which includes the well-characterized proteins FtsK, SpoIIIE, VirB4, and VirD4. We found that a ConE-GFP (green fluorescent protein) fusion associated with the membrane predominantly at the cell poles in ICEBs1donor cells. At least one ICEBs1product likely interacts with ConE to target it to the membrane and cell poles, as ConE-GFP was dispersed throughout the cytoplasm in a strain lacking ICEBs1. We also visualized the subcellular location of ICEBs1. When integrated in the chromosome, ICEBs1was located near midcell along the length of the cell, a position characteristic of that chromosomal region. Following excision, ICEBs1was more frequently found near a cell pole. Excision of ICEBs1also caused altered positioning of at least one component of the replisome. Taken together, our findings indicate that ConE is a critical component of the ICEBs1conjugation machinery, that conjugative transfer of ICEBs1fromB. subtilislikely initiates at a donor cell pole, and that ICEBs1affects the subcellular position of the replisome.
Small Stress Response Proteins in
Escherichia coli
: Proteins Missed by Classical Proteomic Studies
Authors: Hemm Matthew R. , Paul Brian J. , Miranda-Ríos Juan , Zhang Aixia , Soltanzad Nima , Storz Gisela 
Published: September 2009

ABSTRACT

Proteins of 50 or fewer amino acids are poorly characterized in all organisms. The corresponding genes are challenging to reliably annotate, and it is difficult to purify and characterize the small protein products. Due to these technical limitations, little is known about the abundance of small proteins, not to mention their biological functions. To begin to characterize these small proteins in
Escherichia coli
, we assayed their accumulation under a variety of growth conditions and after exposure to stress. We found that many small proteins accumulate under specific growth conditions or are stress induced. For some genes, the observed changes in protein levels were consistent with known transcriptional regulation, such as ArcA activation of the operons encoding
yccB
and
ybgT
. However, we also identified novel regulation, such as Zur repression of
ykgMO
, cyclic AMP response protein (CRP) repression of
azuC
, and CRP activation of
ykgR
. The levels of 11 small proteins increase after heat shock, and induction of at least 1 of these, YobF, occurs at a posttranscriptional level. These results show that small proteins are an overlooked subset of stress response proteins in
E. coli
and provide information that will be valuable for determining the functions of these proteins.
Small RNAs and Small Proteins Involved in Resistance to Cell Envelope Stress and Acid Shock in
Escherichia coli
: Analysis of a Bar-Coded Mutant Collection
Authors: Hobbs Errett C. , Astarita Jillian L. , Storz Gisela 
Published: September 2009

ABSTRACT

More than 80 small regulatory RNAs (sRNAs) and 60 proteins of 16 to 50 amino acids (small proteins) are encoded in the
E
scherichia
coli
genome. The vast majority of the corresponding genes have no known function. We screened 125 DNA bar-coded mutants to identify novel cell envelope stress and acute acid shock phenotypes associated with deletions of genes coding for sRNAs and small proteins. Nine deletion mutants (
ssrA
,
micA
,
ybaM
,
ryeF
,
yqcG
,
sroH
,
ybhT
,
yobF
, and
glmY
) were sensitive to cell envelope stress and two were resistant (
rybB
and
blr
). Deletion mutants of genes coding for four small proteins (
yqgB
,
mgrB
,
yobF
, and
yceO
) were sensitive to acute acid stress. We confirmed each of these phenotypes in one-on-one competition assays against otherwise-wild-type
lacZ
mutant cells. A more detailed investigation of the SsrA phenotype suggests that ribosome release is critical for resistance to cell envelope stress. The bar-coded deletion collection we generated can be screened for sensitivity or resistance to virtually any stress condition.
Reciprocal Regulation between SigK and Differentiation Programs inStreptomyces coelicolor
Authors: Mao Xu-Ming , Zhou Zhan , Hou Xiao-Ping , Guan Wen-Jun , Li Yong-Quan 
Published: September 2009

ABSTRACTHere we reported that deletion of SigK (SCO6520), a sigma factor inStreptomyces coelicolor, caused an earlier switch from vegetative mycelia to aerial mycelia and higher expression ofchpEandchpHthan that in the wild type. Loss of SigK also resulted in accelerated and enhanced production of antibiotics, actinorhodin, and undecylprodigiosin and increased expression ofactII-orf4andredD. These results suggested that SigK had a negative role in morphological transition and secondary metabolism. Furthermore, thesigKpromoter (sigKp) activity gradually increased andsigKexpression was partially dependent on SigK, but this dependence decreased during the developmental course of substrate mycelia. Meanwhile, two potentially nonspecific cleavages occurred between SigK and green fluorescent protein, and the SigK fusion proteins expressed under the constitutive promoterermEp* sharply decreased and disappeared when aerial mycelia emerged. If expressed undersigKp, 3FLAG-SigK showed similar dynamic patterns but did not decrease as sharply as SigK expressed underermEp*. These data suggested that the climbing expression ofsigKmight reduce the prompt degradation of SigK during vegetative hypha development for the proper timing of morphogenesis and that SigK vanished to remove the block for the emergence of aerial mycelia. Thus, we proposed that SigK had inhibitory roles on developmental events and that these inhibitory effects may be released by SigK degradation.
An Interactive Regulatory Network Controls Stress Response inBifidobacterium breveUCC2003
Authors: Zomer Aldert , Fernandez Matilde , Kearney Breda , Fitzgerald Gerald F. , Ventura Marco , van Sinderen Douwe 
Published: September 2009

ABSTRACTMembers of the genusBifidobacteriumare gram-positive bacteria that commonly are found in the gastrointestinal tract (GIT) of mammals, including humans. Because of their perceived probiotic properties, they frequently are incorporated as functional ingredients in food products. From probiotic production to storage and GIT delivery, bifidobacteria encounter a plethora of stresses. To cope with these environmental challenges, they need to protect themselves through stress-induced adaptive responses. We have determined the response ofB. breveUCC2003 to various stresses (heat, osmotic, and solvent) using transcriptome analysis, DNA-protein interactions, and GusA reporter fusions, and we combined these with results from an in silico analysis. The integration of these results allowed the formulation of a model for an interacting regulatory network for stress response inB. breveUCC2003 where HspR controls the SOS response and the ClgR regulon, which in turn regulates and is regulated by HrcA. This model of an interacting regulatory network is believed to represent the paradigm for stress adaptation in bifidobacteria.
Atypical Protein Kinase Cι Is Required for Bronchioalveolar Stem Cell Expansion and Lung Tumorigenesis
Authors: Regala Roderick P. , Davis Rebecca K. , Kunz Alyssa , Khoor Andras , Leitges Michael , Fields Alan P. 
Published: September 2009

Abstract
Protein kinase Cι (PKCι) is an oncogene required for maintenance of the transformed phenotype of non–small cell lung cancer cells. However, the role of PKCι in lung tumor development has not been investigated. To address this question, we established a mouse model in which oncogenic KrasG12D is activated by Cre-mediated recombination in the lung with or without simultaneous genetic loss of the mouse PKCι gene, Prkci. Genetic loss of Prkci dramatically inhibits Kras-initiated hyperplasia and subsequent lung tumor formation in vivo. This effect correlates with a defect in the ability of Prkci-deficient bronchioalveolar stem cells to undergo Kras-mediated expansion and morphologic transformation in vitro and in vivo. Furthermore, the small molecule PKCι inhibitor aurothiomalate inhibits Kras-mediated bronchioalveolar stem cell expansion and lung tumor growth in vivo. Thus, Prkci is required for oncogene-induced expansion and transformation of tumor-initiating lung stem cells. Furthermore, aurothiomalate is an effective antitumor agent that targets the tumor-initiating stem cell niche in vivo. These data have important implications for PKCι as a therapeutic target and for the clinical use of aurothiomalate for lung cancer treatment. [Cancer Res 2009;69(19):7603–11]
The Soering reshold: Why Only Fundamental Values Prohibit Refoulement in ECHR Case Law
Authors: Battjes Hemme 
Published: September 2009

AbstractAccording to ECHR case-law, the Convention prohibits expulsion if violations of Articles 2 and 3 are risked upon return. Feared violations of other rights such as the freedom of religion do normally not prohibit expulsion. This article explores how the Court delimits violations that prohibit expulsion from those that do not, and which reasons the Court has put forward for justifying this distinction. It focuses on the consistency in the Court's reasoning. It is submitted that balancing human rights to inter alia the economic well-being of the Contacting states determines the outcome of expulsion cases, although this balancing is in many cases invisible, and that this balancing test rests upon the relevance of the alien status of those who invoke the prohibition on expulsion, although this relevance has not been substantiated in the case-law.
Still Silencing the Racism Suffered by Migrants . . . The Limits of Current Developments under Article 14 ECHR
Authors: Dembour Marie-Bénédicte 
Published: September 2009

AbstractThe European Court of Human Rights has recently developed its jurisprudence related to racial discrimination in highly significant ways. The Court has rightly been applauded for abandoning its requirement that racial discrimination be proved 'beyond reasonable doubt' and for endorsing the concept of indirect discrimination, allowing it, in the last five years, to begin to find states from 'eastern Europe' in violation of the Convention for having discriminated against especially Roma applicants. While welcome, these new developments should not detract from the need to continue asking difficult questions, including the following: why has it taken decades for the Court to start finding a violation of Article 14 on grounds of race? Why are cases, such as Menson v. United Kingdom concerning the slow reaction of the police in investigating the lethal attack of a black man, not found admissible? Can we expect the Court, created in a region which largely built itself upon colonialism, to generate mechanisms fit to tackle racism? In the past, judges themselves have provided the most virulent critique of the Court's inability to tackle racism. Migrants still remain to benefit from their progressive stance in relation to Article 14 claims based on grounds of race.
Love Thy Neighbour: Family Reunification and the Rights of Insiders
Authors: de Hart Betty 
Published: September 2009

AbstractThis article looks at the extent and way in which the European Court of Human Rights takes the interests of insider spouses (citizens or permanent residents) into account in Article 8 ECHR cases (right to family life). It uses Caren's three moral principles for family reunification policies as an analysing tool for the evaluation of the Court's first admission and expulsion cases, and looks at the underlying notions of gender and ethnicity. The author concludes that insiders' interests play only a marginal role in the case law and offers several explanations. Although the Court has acknowledged that family reunification is about insiders, it has not taken the consequences of such a position into account. It does not look at the ties of the insider spouse to his or her country of citizenship or residence. It sees the relationships of insider women with migrant partners as a more serious threat to restrictive immigration policies than relationships of insider men with migrant women. Furthermore, the Court thinks of nation-states as closed units to which migrants may be admitted as an exception to the rule, and does not acknowledge that insiders develop family relations with outsiders either within or outside the nation-state.
The Exclusiveness of Inclusion: On the Boundaries of Human Rights in Protecting Transnational and Second Generation Migrants
Authors: Farahat Anuscheh 
Published: September 2009

AbstractThis article analyses the treatment of so-called transnational migrants in expulsion cases reviewed under Article 8 of the European Convention on Human Rights before the European Court of Human Rights (hereinafter: the Court). By regularly crossing national borders and maintaining cultural and social ties to more than one country these migrants are in fact not effectively protected by the Court. This disadvantaging treatment can be explained as being the result of the Court's doctrine of margin of appreciation which allows domestic political preference in immigration policy to dominate the balancing process before the Court. The margin of appreciation doctrine is interpreted as the Court's way of dealing with the more general tension it faces in acting as a guardian on the one hand and respecting domestic legislation on the other. This tension is strengthened by the institutional arrangement under which the Court is acting. Against this background, this article submits two possible amendments on the doctrinal and procedural level, suggesting that the Court should follow a more inclusive reasoning and should replace the margin of appreciation doctrine by the concept of core content.
Structural Instability: Strasbourg Case Law on Children's Family Reunion
Authors: Spijkerboer Thomas 
Published: September 2009

AbstractIn this article, the case law of the European Court of Human Rights on children's family reunion is examined. The argument is that the Court's case law is necessarily inconsistent. This is so in part as a consequence of the structure of international legal argument, and partly as a consequence of the seeming normative conflict about the legitimacy of migration control. On both points, the Court is torn between two equally legitimate and equally untenable extremes, which forces the Court to take a centrist position and to acknowledge both the legitimacy and the untenable nature of any position. The main part of the article analyses how this takes shape in the legal technicalities in the judgements under review.
Against All Odds: How Single and Divorced Migrant Mothers were Eventually able to Claim their Right to Respect for Family Life
Authors: van Walsum Sarah 
Published: September 2009

AbstractFeminist and post-colonial theorists challenge the supposed neutrality of international human rights law which, in their view, should be seen as a product of asymmetrical power relations. On the basis of this premise, it seems unlikely that single and divorced migrant mothers from outside of the EU will be able to mobilize international human rights law to their advantage. And yet, after twenty years of litigation, single and divorced migrant mothers in the Netherlands are now finally able to claim their right to respect for family life and reunite with children left behind in their countries of origin. This chapter seeks to explain how this increase in human rights protection could come about. While some litigants are less powerful than others, they do not always stand alone. Increasing the scope of analyses makes it possible to include case law produced by more powerful actors. Their gains can offer strategic opportunities to those less powerful.