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Biomedical subjects

Susan Jones

Publications and source records attributed to Susan Jones.

16 recordsLinked to original sources
PubMed2005

Molecular determinants for PspA-mediated repression of the AAA transcriptional activator PspF.

The Escherichia coli phage shock protein system (pspABCDE operon and pspG gene) is induced by numerous stresses related to the membrane integrity state. Transcription of the psp genes requires the RNA polymerase containing the sigma(54) subunit and the AAA transcriptional activator PspF. PspF belongs to an atypical class of sigma(54) AAA activators in that it lacks an N-terminal regulatory domain and is instead negatively regulated by another regulatory protein, PspA. PspA therefore represses its own expression. The PspA protein is distributed between the cytoplasm and the inner membrane fraction. In addition to its transcriptional inhibitory role, PspA assists maintenance of the proton motive force and protein export. Several lines of in vitro evidence indicate that PspA-PspF interactions inhibit the ATPase activity of PspF, resulting in the inhibition of PspF-dependent gene expression. In this study, we characterize sequences within PspA and PspF crucial for the negative effect of PspA upon PspF. Using a protein fragmentation approach, we show that the integrity of the three putative N-terminal alpha-helical domains of PspA is crucial for the role of PspA as a negative regulator of PspF. A bacterial two-hybrid system allowed us to provide clear evidence for an interaction in E. coli between PspA and PspF in vivo, which strongly suggests that PspA-directed inhibition of PspF occurs via an inhibitory complex. Finally, we identify a single PspF residue that is a binding determinant for PspA.

Bacterial Proteins↗
PubMed2003

A systematic investigation into the effect of protein destabilisation on beta 2-microglobulin amyloid formation.

Beta-2-microglobulin (beta(2)m) has been shown to form amyloid fibrils with distinct morphologies under acidic conditions in vitro. Short, curved fibrils (<600 nm in length), form rapidly without a lag phase, with a maximum rate at pH 3.5. By contrast, fibrils with a long (approximately 1 microm), straight morphology are produced by incubation of the protein at pH< or =3.0. Both fibril types display Congo red birefringence, bind Thioflavin-T and have X-ray fibre diffraction patterns consistent with a cross-beta structure. In order to investigate the role of different partially folded states in generating fibrils of each type, and to probe the effect of protein stability on amyloid formation, we have undertaken a detailed mutagenesis study of beta(2)m. Thirteen variants containing point mutations in different regions of the native protein were created and their structure, stability and fibril forming propensities were investigated as a function of pH. By altering the stability of the native protein in this manner, we show that whilst destabilisation of the native state is important in the generation of amyloid fibrils, population of specific denatured states is a pre-requisite for amyloid formation from this protein. Moreover, we demonstrate that the formation of fibrils with different morphologies in vitro correlates with the relative population of different precursor states.

Amyloid↗
PubMed2003

Role of the N and C-terminal strands of beta 2-microglobulin in amyloid formation at neutral pH.

Beta 2-microglobulin (beta(2)m) is known to form amyloid fibrils de novo in vitro under acidic conditions (below pH 4.8). Fibril formation at neutral pH, however, has only been observed by deletion of the N-terminal six residues; by the addition of pre-assembled seeds; or in the presence of Cu(2+). Based on these observations, and other structural data, models for fibril formation of beta(2)m have been proposed that involve the fraying of the N and C-terminal beta-strands and the consequent loss of edge strand protective features. Here, we examine the role of the N and C-terminal strands in the initiation of fibrillogenesis of beta(2)m by creating point mutations in strands A and G and comparing the properties of the resulting proteins with variants containing similar mutations elsewhere in the protein. We show that truncation of buried hydrophobic side-chains in strands A and G promotes rapid fibril formation at neutral pH, even in unseeded reactions, and increases the rate of fibril formation under acidic conditions. By contrast, similar mutations created in the remaining seven beta-strands of the native protein have little effect on the rate or pH dependence of fibril formation. The data are consistent with the view that perturbation of the N and C-terminal edge strands is an important feature in the generation of assembly-competent states of beta(2)m.

Amyloid↗
PubMed2003

Using structural motif templates to identify proteins with DNA binding function.

This work describes a method for predicting DNA binding function from structure using 3-dimensional templates. Proteins that bind DNA using small contiguous helix-turn-helix (HTH) motifs comprise a significant number of all DNA-binding proteins. A structural template library of seven HTH motifs has been created from non-homologous DNA-binding proteins in the Protein Data Bank. The templates were used to scan complete protein structures using an algorithm that calculated the root mean squared deviation (rmsd) for the optimal superposition of each template on each structure, based on C(alpha) backbone coordinates. Distributions of rmsd values for known HTH-containing proteins (true hits) and non-HTH proteins (false hits) were calculated. A threshold value of 1.6 A rmsd was selected that gave a true hit rate of 88.4% and a false positive rate of 0.7%. The false positive rate was further reduced to 0.5% by introducing an accessible surface area threshold value of 990 A2 per HTH motif. The template library and the validated thresholds were used to make predictions for target proteins from a structural genomics project.

Algorithms↗
PubMed2003

Sequence variation in the CHAT locus shows no association with late-onset Alzheimer's disease.

There is substantial evidence for a susceptibility gene for late-onset Alzheimer's disease (AD) on chromosome 10. One of the characteristic features of AD is the degeneration and dysfunction of the cholinergic system. The genes encoding choline acetyltransferase (ChAT) and its vesicular transporter (VAChT), CHAT and SLC18A3 respectively, map to the linked region of chromosome 10 and are therefore both positional and obvious functional candidate genes for late-onset AD. We have screened both genes for sequence variants and investigated each for association with late-onset AD in up to 500 late-onset AD cases and 500 control DNAs collected in the UK. We detected a total of 17 sequence variants. Of these, 14 were in CHAT, comprising three non-synonymous variants (D7N in the S exon, A120T in exon 5 and L243F in exon 8), one synonymous change (H547H), nine single-nucleotide polymorphisms in intronic, untranslated or promoter regions, and a variable number of tandem repeats in intron 7. Three non-coding SNPs were detected in SLC18A3. None demonstrated any reproducible association with late-onset AD in our samples. Levels of linkage disequilibrium were generally low across the CHAT locus but two of the coding variants, D7N and A120T, proved to be in complete linkage disequilibrium.

Aged↗
PubMed2003

Amyloid-forming peptides from beta2-microglobulin-Insights into the mechanism of fibril formation in vitro.

Beta(2)-Microglobulin (beta(2)m) is one of over 20 proteins known to be involved in human amyloid disease. Peptides equivalent to each of the seven beta-strands of the native protein, together with an eighth peptide (corresponding to the most stable region in the amyloid precursor conformation formed at pH 3.6, that includes residues in the native strand E plus the eight succeeding residues (named peptide E')), were synthesised and their ability to form fibrils investigated. Surprisingly, only two sequences, both of which encompass the region that forms strand E in native beta(2)m, are capable of forming amyloid-like fibrils in vitro. These peptides correspond to residues 59-71 (peptide E) and 59-79 (peptide E') of intact beta(2)m. The peptides form fibrils under the acidic conditions shown previously to promote amyloid formation from the intact protein (pH <5 at low and high ionic strength), and also associate to form fibrils at neutral pH. Fibrils formed from these two peptides enhance fibrillogenesis of the intact protein. No correlation was found between secondary structure propensity, peptide length, pI or hydrophobicity and the ability of the peptides to associate into amyloid-like fibrils. However, the presence of a relatively high content of aromatic side-chains correlates with the ability of the peptides to form amyloid fibrils. On the basis of these results we propose that residues 59-71 may be important in the self-association of partially folded beta(2)m into amyloid fibrils and discuss the relevance of these results for the assembly mechanism of the intact protein in vitro.

Amino Acid Sequence↗
PubMed2003

Preoperative teaching and hysterectomy outcomes.

This study used a theoretical model to determine whether an efficacy-enhancing teaching protocol was effective in improving immediate postoperative behaviors and selected short- and long-term health outcomes in women who underwent abdominal hysterectomies. The model used was the self-efficacy theory of Albert Bandura, PhD. One hundred eight patients in a 486-bed teaching hospital in the Midwest who underwent hysterectomies participated. The participation rate was 85%, and the attrition rate was 17% during the six-month study. The major finding was that participants in the efficacy-enhancing teaching group ambulated significantly longer than participants in the usual care group. This is an important finding because the most prevalent postoperative complications after hysterectomy are atelectasis, pneumonia, paralytic ileus, and deep vein thrombosis, and postoperative ambulation has been shown to decrease or prevent all of these complications. This finding could affect the overall health status of women undergoing hysterectomies.

Adult↗
PubMed2002

Schizophrenia and functional polymorphisms in the MAOA and COMT genes: no evidence for association or epistasis.

Several lines of evidence suggest that psychosis is associated with altered dopaminergic neurotransmission. Dopamine is catabolized by monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT). We hypothesized that the genes encoding MAOA and COMT might contain genetic variation conferring increased risk to schizophrenia. In order to test this hypothesis, we genotyped the 941T > G and the promoter VNTR polymorphisms in the MAOA gene and the V158M COMT polymorphism in 346 DSMIV schizophrenics and 334 controls. We also genotyped the-287A > G COMT promoter polymorphism in 177 schizophrenics and 173 controls. No significant differences were found in allele or genotype frequencies between affecteds and controls for any of the polymorphisms. As both genes are involved in degrading catecholamines, we also sought evidence for additive and epistatic effects but none was observed. Our data, therefore, do not support the hypothesis that genetic variation in MAOA and COMT is involved individually or in combination in the etiology of schizophrenia.

Adult↗
PubMed2002

Mechanism of action of the Escherichia coli phage shock protein PspA in repression of the AAA family transcription factor PspF.

The PspA protein, a negative regulator of the Escherichia coli phage shock psp operon, is produced when virulence factors are exported through secretins in many Gram-negative pathogenic bacteria and its homologue in plants, VIPP1, plays a critical role in thylakoid biogenesis, essential for photosynthesis. Activation of transcription by the enhancer-dependent bacterial sigma(54) containing RNA polymerase occurs through ATP hydrolysis-driven protein conformational changes enabled by activator proteins that belong to the large AAA(+) mechanochemical protein family. We show that PspA directly and specifically acts upon and binds to the AAA(+) domain of the PspF transcription activator. Interactions involving PspF and nucleotide are changed by the action of PspA. These changes and the complexes that form between PspF and PspA can explain how PspA exerts its negative effects upon transcription activated by PspF, and are of significance when considering how activities of other AAA(+) proteins might be controlled.

Adenosine Triphosphatases↗
PubMed2002

Food cravings and aversions during pregnancy: relationships with nausea and vomiting.

Food cravings and food aversions are common during pregnancy. A mechanism that may explain these changes in food preference is taste aversion learning. Accordingly, this study examined the temporal association between the first occurrences of nausea, vomiting, food cravings and food aversions during pregnancy. Ninety-nine women completed a questionnaire that asked about the occurrence, timing of first onset, duration, strength and targets of these symptoms. Nausea and vomiting were reported by 80% and 56% of the women, food cravings and aversions by 61% and 54% respectively. Although more women experienced both food cravings and aversions than either symptom alone, cravings and aversions were statistically unrelated. There was a significant positive correlation between week of onset of nausea and of aversions. In 60% of women reporting both nausea and food aversions, the first occurrence of each happened in the same week of pregnancy. No such association was found for cravings. These retrospective accounts provide good support for taste aversion learning as a mechanism for the development of some but not all food aversions during pregnancy. Prospective data are needed to confirm these temporal relationships and to assist understanding of the emergence of food cravings.

Adult↗
PubMed2000

Characteristics of staffed community housing services for people with learning disabilities: a stratified random sample of statutory, voluntary and private agency provision.

Within the staffed housing model relatively little is known about the characteristics of different types of provider agency. Data on size, homeliness and physical integration of settings, organisational culture, working methods, staffing levels and resident characteristics, were collected on a stratified random sample of provision in South-West England and Wales. Provider agencies did not differ significantly on three of the four variables relating to residents' characteristics. Nor did they differ in terms of the homeliness or physical integration of settings. However, there were significant differences between providers on the important variables of working methods and staffing levels. Resident ability correlated with staffing levels and organisational culture, but not with staff working methods. The results and their implications are discussed in the context of other research which has used the same measures.

Journal Article↗
PubMedDate not supplied

Stimulated production of vowel-like LX-waveforms and spectral damping in the absence of phonation.

Electrical impedance 'LX' waveforms measured across the neck at the thyroid level during phonation are known to be correlated with vocal fold movement. Changes in vocal fold contact are thought to be the cause of this phenomenon though emerging applications in radiotherapy indicate that changes in the configuration of both fold and neck tissues are correlated with LX waveform shape. In this paper it is shown that a two-stage tissue damping model with controlled bandpass and passive low pass components is consistent with evidence from gradually degraded, controlled phonation. In particular it is shown that an externally applied stimulus to the vertebral processes of the neck can produce similar impedance waveforms in the absence of phonation and hence no controlled fold contact. It is postulated that this is initial evidence suggesting that both pressure waves and vocal fold contact components contribute to the production of the classical 'LX' waveform.

Electric Impedance↗
PubMedDate not supplied

A clinical pathway for pediatric gastroenteritis.

Gastroenteritis is one of the most common reasons for hospitalization in the United States for children under the age of 5 years. Second only to respiratory problems, the cost of providing care for these children is estimated to exceed $2 billion dollars annually ( Burkhart, 1999; Prescilla, 2002). This article reviews the causes of gastroenteritis as well as the 1996 American Academy of Pediatrics Guidelines for treatment of gastroenteritis. These guidelines and more recently published literature were used to develop a clinical pathway to improve the care of pediatric patients admitted to the hospital with gastroenteritis. The article discusses the importance of clinical pathways and the process of implementation of a pathway for pediatric gastroenteritis. Additionally, the article provides a parent teaching tool to address recurrent questions parents have related to home management of a child with gastroenteritis. Useful web sites for resource information related to gastroenteritis are provided as well.

Child, Preschool↗