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1.
Dig Liver Dis ; 56(3): 484-494, 2024 Mar.
Article in English | MEDLINE | ID: mdl-37968144

ABSTRACT

BACKGROUND: Most ultrasound-based methods for assessing liver fibrosis still need further validation with liver biopsy used as gold standard to assess their accuracy. AIMS: To assess accuracy of three shear wave elastography (SWE) methods: 1) Philips Elast Point Quantification (ElastPQTM), 2) Siemens Virtual TouchTM Quantification (VTQ) acoustic radiation force impulse (ARFI), and 3) transient elastography (TE) measured by Echosens FibroscanTM. METHODS: 160 patients underwent liver stiffness measurements (LSM) with three SWE methods immediately prior to liver biopsy. RESULTS: The number of LSM required for reliable studies could be reduced to 6 for ElastPQ and to 7 for VTQ from standard recommendations of 10. Significant fibrosis and interquartile range/median (IQR/M)> 30 were independent predictors for lower reliability for detection of liver fibrosis. Ordinal logistic regression corrected for age showed that there was a significant interaction between steatosis (p = 0.008) and lobular inflammation (p = 0.04) and VTQ (ARFI) and between lobular inflammation and TE (p = 0.006). CONCLUSIONS: We showed variations in SWE measurements using different ARFI technologies. TE and ElastPQ achieved good diagnostic performance, whereas VTQ showed lower diagnostic accuracy. The number of measurements required for reliable studies can be reduced to 6 for ElastPQ and to 7 for VTQ, which have important clinical implications.


Subject(s)
Elasticity Imaging Techniques , Liver Diseases , Humans , Elasticity Imaging Techniques/methods , Reproducibility of Results , Liver Diseases/diagnosis , Liver/diagnostic imaging , Liver/pathology , Liver Cirrhosis/diagnostic imaging , Liver Cirrhosis/pathology , Biopsy , Inflammation/pathology
3.
Hepat Med ; 15: 51-61, 2023.
Article in English | MEDLINE | ID: mdl-37325088

ABSTRACT

Purpose: The Controlled Attenuation Parameter (CAP score) is based on ultrasonic properties of retropropagated radiofrequency signals acquired by FibroscanTM (Echosens, Paris, France). Since ultrasound propagation is influenced by the presence of fat, CAP score was developed to quantify steatosis. The aim of this study was to delineate the accuracy of CAP in diagnosing hepatic steatosis, compared to the gold standard of liver biopsy. Patients and Methods: A total of 150 patients underwent same-day liver biopsy and measurement of hepatic steatosis with Fibroscan. Only examinations with 10 satisfactory measurements, and an inter-quartile range of less than 30% of the median liver stiffness values were included for data analysis. Histological staging was then correlated with median values and Spearman correlation calculated. P values of <0.05 were considered statistically significant. Results: For diagnosis of hepatic steatosis (HS), CAP could predict the steatosis S2 with AUROC 0.815 (95% CI 0.741-0.889), sensitivity (0.81) and specificity (0.73) when the optimal cut-off value was set at 288 dB/m. CAP detected histological grade S3 with AUROC 0.735 (95% CI 0.618-0.851), sensitivity (0.71) and specificity (0.74), with a cut-off value of 330 dB/m. The AUROC for steatosis grade S1 was 0.741 (95% CI 0.650-0.824), with a cut-off value of 263 dB/m with sensitivity 0.75 and specificity 0.70. Univariate analysis showed a correlation between CAP and diabetes (p 0.048). Conclusion: The performance of CAP to diagnose steatosis severity decreases as steatosis progresses. CAP is associated with diabetes but not other clinical factors and parameters of the metabolic syndrome.

5.
Br J Nutr ; 129(3): 406-415, 2023 02 14.
Article in English | MEDLINE | ID: mdl-35152926

ABSTRACT

Malnutrition and sarcopenia are prevalent in patients with head and neck squamous cell carcinoma (HNSCC). Pre-treatment sarcopenia and adverse oncological outcomes in this population are well described. The impact of myosteatosis and post-treatment sarcopenia is less well known. Patients with HNSCC (n = 125) undergoing chemoradiotherapy, radiotherapy alone and/or surgery were assessed for sarcopenia and myosteatosis, using cross-sectional computed tomography (CT) imaging at the third lumbar (L3) vertebra, at baseline and 3 months post-treatment. Outcomes were overall survival (OS) at 12 months and 5 years post-treatment. One hundred and one participants had a CT scan evaluable at one or two time points, of which sixty-seven (66 %) participants were sarcopenic on at least one time point. Reduced muscle attenuation affected 93 % (n = 92) pre-treatment compared with 97 % (n = 90) post-treatment. Five-year OS favoured those without post-treatment sarcopenia (hazard ratio, HR 0·37, 95 % CI 0·16, 0·88, P = 0·06) and those without both post-treatment myosteatosis and sarcopenia (HR 0·33, 95 % CI 0·13, 0·83, P = 0·06). Overall, rates of myosteatosis were high at both pre- and post-treatment time points. Post-treatment sarcopenia was associated with worse 5-year OS, as was post-treatment sarcopenia in those who had myosteatosis. Post-treatment sarcopenia should be evaluated as an independent risk factor for decreased long-term survival post-treatment containing radiotherapy (RT) for HNSCC.


Subject(s)
Head and Neck Neoplasms , Sarcopenia , Humans , Sarcopenia/complications , Squamous Cell Carcinoma of Head and Neck/complications , Squamous Cell Carcinoma of Head and Neck/therapy , Squamous Cell Carcinoma of Head and Neck/pathology , Muscle, Skeletal/pathology , Cross-Sectional Studies , Body Composition , Head and Neck Neoplasms/complications , Head and Neck Neoplasms/radiotherapy , Retrospective Studies , Prognosis
7.
Health Technol Assess ; 26(40): 1-144, 2022 Oct.
Article in English | MEDLINE | ID: mdl-36300825

ABSTRACT

BACKGROUND: Around 7500 people are diagnosed with non-muscle-invasive bladder cancer in the UK annually. Recurrence following transurethral resection of bladder tumour is common, and the intensive monitoring schedule required after initial treatment has associated costs for patients and the NHS. In photodynamic diagnosis, before transurethral resection of bladder tumour, a photosensitiser that is preferentially absorbed by tumour cells is instilled intravesically. Transurethral resection of bladder tumour is then conducted under blue light, causing the photosensitiser to fluoresce. Photodynamic diagnosis-guided transurethral resection of bladder tumour offers better diagnostic accuracy than standard white-light-guided transurethral resection of bladder tumour, potentially reducing the chance of subsequent recurrence. OBJECTIVE: The objective was to assess the clinical effectiveness and cost-effectiveness of photodynamic diagnosis-guided transurethral resection of bladder tumour. DESIGN: This was a multicentre, pragmatic, open-label, parallel-group, non-masked, superiority randomised controlled trial. Allocation was by remote web-based service, using a 1 : 1 ratio and a minimisation algorithm balanced by centre and sex. SETTING: The setting was 22 NHS hospitals. PARTICIPANTS: Patients aged ≥ 16 years with a suspected first diagnosis of high-risk non-muscle-invasive bladder cancer, no contraindications to photodynamic diagnosis and written informed consent were eligible. INTERVENTIONS: Photodynamic diagnosis-guided transurethral resection of bladder tumour and standard white-light cystoscopy transurethral resection of bladder tumour. MAIN OUTCOME MEASURES: The primary clinical outcome measure was the time to recurrence from the date of randomisation to the date of pathologically proven first recurrence (or intercurrent bladder cancer death). The primary health economic outcome was the incremental cost per quality-adjusted life-year gained at 3 years. RESULTS: We enrolled 538 participants from 22 UK hospitals between 11 November 2014 and 6 February 2018. Of these, 269 were allocated to photodynamic diagnosis and 269 were allocated to white light. A total of 112 participants were excluded from the analysis because of ineligibility (n = 5), lack of non-muscle-invasive bladder cancer diagnosis following transurethral resection of bladder tumour (n = 89) or early cystectomy (n = 18). In total, 209 photodynamic diagnosis and 217 white-light participants were included in the clinical end-point analysis population. All randomised participants were included in the cost-effectiveness analysis. Over a median follow-up period of 21 months for the photodynamic diagnosis group and 22 months for the white-light group, there were 86 recurrences (3-year recurrence-free survival rate 57.8%, 95% confidence interval 50.7% to 64.2%) in the photodynamic diagnosis group and 84 recurrences (3-year recurrence-free survival rate 61.6%, 95% confidence interval 54.7% to 67.8%) in the white-light group (hazard ratio 0.94, 95% confidence interval 0.69 to 1.28; p = 0.70). Adverse event frequency was low and similar in both groups [12 (5.7%) in the photodynamic diagnosis group vs. 12 (5.5%) in the white-light group]. At 3 years, the total cost was £12,881 for photodynamic diagnosis-guided transurethral resection of bladder tumour and £12,005 for white light. There was no evidence of differences in the use of health services or total cost at 3 years. At 3 years, the quality-adjusted life-years gain was 2.094 in the photodynamic diagnosis transurethral resection of bladder tumour group and 2.087 in the white light group. The probability that photodynamic diagnosis-guided transurethral resection of bladder tumour was cost-effective was never > 30% over the range of society's cost-effectiveness thresholds. LIMITATIONS: Fewer patients than anticipated were correctly diagnosed with intermediate- to high-risk non-muscle-invasive bladder cancer before transurethral resection of bladder tumour and the ratio of intermediate- to high-risk non-muscle-invasive bladder cancer was higher than expected, reducing the number of observed recurrences and the statistical power. CONCLUSIONS: Photodynamic diagnosis-guided transurethral resection of bladder tumour did not reduce recurrences, nor was it likely to be cost-effective compared with white light at 3 years. Photodynamic diagnosis-guided transurethral resection of bladder tumour is not supported in the management of primary intermediate- to high-risk non-muscle-invasive bladder cancer. FUTURE WORK: Further work should include the modelling of appropriate surveillance schedules and exploring predictive and prognostic biomarkers. TRIAL REGISTRATION: This trial is registered as ISRCTN84013636. FUNDING: This project was funded by the National Institute for Health and Care Research ( NIHR ) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 26, No. 40. See the NIHR Journals Library website for further project information.


Around 7500 people are diagnosed with early-stage bladder cancer in the UK each year. Early bladder cancer is contained within the bladder and has not yet invaded the bladder's muscle wall or spread elsewhere in the body. The cancer will return (recur) in around half of people after initial treatment and they have to attend hospital for regular check-ups, with costs to both them and the NHS. The first step in treating early bladder cancer is surgery to remove the tumour. This surgery is normally performed under white light. Photodynamic diagnosis is a new technique in which a liquid is put into the patient's bladder before surgery and a blue light is used during the operation. This causes the bladder cancer to fluoresce so that it can be seen more easily by the surgeon. The Photodynamic versus white-light-guided resection of first diagnosis non-muscle-invasive bladder cancer ( PHOTO ) trial aimed to find out whether or not using photodynamic diagnosis at initial surgery would reduce how often the cancer recurred and whether or not this could reduce the cost of treating early bladder cancer. A total of 538 people with early bladder cancer who had a medium to high chance of their cancer returning after treatment were enrolled in the PHOTO trial. They were included in one of two treatment groups, at random: 269 had photodynamic surgery and 269 had standard white-light surgery. People in both groups were monitored regularly for any recurrences, with further treatment as appropriate. After 3 years, 4 out of 10 people in each group had a recurrence of their bladder cancer. We found no difference between the treatment groups in the number of people with recurrences. We found no evidence of a benefit to patients, and the total costs of photodynamic surgery were higher than those of standard white light. We therefore recommend that it is no longer used in the treatment of this group of patients.


Subject(s)
Urinary Bladder Neoplasms , Humans , Biomarkers , Cost-Benefit Analysis , Quality of Life , Quality-Adjusted Life Years , Technology Assessment, Biomedical , Urinary Bladder Neoplasms/diagnosis , Urinary Bladder Neoplasms/surgery , Light , Photochemotherapy
8.
Biomol NMR Assign ; 14(1): 87-91, 2020 04.
Article in English | MEDLINE | ID: mdl-31916136

ABSTRACT

The Ral proteins (RalA and RalB) are small G proteins of the Ras family that have been implicated in exocytosis, endocytosis, transcriptional regulation and mitochondrial fission, as well as having a role in tumourigenesis. RalA and RalB are activated downstream of the master regulator, Ras, which causes the nucleotide exchange of GDP for GTP. Here we report the 1H, 15 N and 13C resonance assignments of RalA in its active form bound to the GTP analogue GMPPNP. We also report the backbone assignments of RalA in its inactive, GDP-bound form. The assignments give insight into the switch regions, which change conformation upon nucleotide exchange. These switch regions are invisible in the spectra of the active, GMPPNP bound form but the residues proximal to the switches can be monitored. RalA is also an important drug target due to its over activation in some cancers and these assignments will be extremely useful for NMR-based screening approaches.


Subject(s)
Monomeric GTP-Binding Proteins/chemistry , Nuclear Magnetic Resonance, Biomolecular , ral GTP-Binding Proteins/chemistry , Guanosine Diphosphate/chemistry , Protein Conformation
9.
J Med Ethics ; 44(8): 513-517, 2018 Aug.
Article in English | MEDLINE | ID: mdl-29776978

ABSTRACT

The Republic of Ireland has some of the most restrictive abortion legislation in the world which grants to the 'unborn' an equal right to life to that of the pregnant woman. This article outlines recent developments in the public discourse on abortion in Ireland and explains the particular cultural and religious context that informs the ethical case for access to abortion services. Our perspective rests on respect for two very familiar moral principles - autonomy and justice - which are at the centre of social and democratic societies around the world. This article explains the context for the deployment of these concepts in order to support the claim that the current legislation and its operationalisation in clinical practice poses serious risks to the health, lives and well-being of pregnant women, tramples on their autonomy rights and requires of them a self-sacrifice that is unreasonable and unjust.


Subject(s)
Abortion, Induced/ethics , Abortion, Induced/legislation & jurisprudence , Health Services Accessibility/ethics , Health Services Accessibility/legislation & jurisprudence , Women's Rights/ethics , Women's Rights/legislation & jurisprudence , Female , Humans , Ireland , Pregnancy
10.
Article in English | MEDLINE | ID: mdl-26893900

ABSTRACT

Within the dental hospital setting, it is a frequent occurrence to find residual cement contaminating instruments in a newly opened kit having undergone the decontamination cycle. Any instrument found to be contaminated then cannot be used, as the area underneath the cement is not sterile. This in itself has several repercussions. These include: cross-contamination, since there is a chance that the cement will be removed and the contaminated instrument used; cost, as each new kit that will be opened due to contaminated instruments will incur decontamination costs; and finally time, which most importantly has an impact on patient experience. Our baseline data recording focussed on finding out the severity of the problem, which instruments were most affected, and how this affected patient treatment, using a questionnaire. Within the paediatric department, 27% of examination kits contained a contaminated instrument, almost one third of all kits used. This quality improvement project utilized a poster and team huddle discussions to raise awareness of the problem and successfully reduced the number of contaminated instrument kits to 7% over a period of four weeks.

11.
World J Gastroenterol ; 21(29): 8920-6, 2015 Aug 07.
Article in English | MEDLINE | ID: mdl-26269682

ABSTRACT

AIM: To assess the prevalence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection and association with drug induced liver injury (DILI) in patients undergoing anti-tuberculosis (TB) therapy. METHODS: Four hundred and twenty nine patients with newly diagnosed TB - either active disease or latent infection - who were due to commence anti-TB therapy between September 2008 and May 2011 were included. These patients were prospectively tested for serological markers of HBV, HCV and human immunodeficiency virus (HIV) infections - hepatitis B core antigen (HBcAg), hepatitis B surface antigen (HBsAg), hepatitis B e antigen, IgG and IgM antibody to HBcAg (anti-HBc), HCV IgG antibody and HIV antibody using a combination of enzyme-linked immunosorbent assay, Western blot assay and polymerase chain reaction techniques. Patients were reviewed at least monthly during the TB treatment initiation phase. Liver function tests were measured prior to commencement of anti-TB therapy and 2-4 wk later. Liver function tests were also performed at any time the patient had significant nausea, vomiting, rash, or felt non-specifically unwell. Fisher's exact test was used to measure significance in comparisons of proportions between groups. A P value of less than 0.05 was considered statistically significant. RESULTS: Of the 429 patients, 270 (62.9%) had active TB disease and 159 (37.1%) had latent TB infection. 61 (14.2%) patients had isolated anti-HBc positivity, 11 (2.6%) were also HBsAg positive and 7 (1.6%) were HCV-antibody positive. 16/270 patients with active TB disease compared to 2/159 patients with latent TB infection had markers of chronic viral hepatitis (HBsAg or HCV antibody positive; P = 0.023). Similarly the proportion of HBsAg positive patients were significantly greater in the active vs latent TB infection group (10/43 vs 1/29, P = 0.04). The prevalence of chronic HBV or HCV was significantly higher than the estimated United Kingdom prevalence of 0.3% for each. We found no association between DILI and presence of serological markers of HBV or HCV. Three (5.3%) patients with serological markers of HBV or HCV infection had DILI compared to 25 (9.5%) patients without; P = 0.04. CONCLUSION: Viral hepatitis screening should be considered in TB patients. DILI risk was not increased in patients with HBV/HCV.


Subject(s)
Coinfection , Hepatitis B/epidemiology , Hepatitis C/epidemiology , Latent Tuberculosis/epidemiology , Adolescent , Adult , Aged , Aged, 80 and over , Antitubercular Agents/adverse effects , Biomarkers/blood , Chemical and Drug Induced Liver Injury/diagnosis , Chemical and Drug Induced Liver Injury/epidemiology , Female , Hepatitis B/diagnosis , Hepatitis C/diagnosis , Humans , Latent Tuberculosis/diagnosis , Latent Tuberculosis/drug therapy , Liver Function Tests , Male , Mass Screening , Middle Aged , Predictive Value of Tests , Prevalence , Prospective Studies , Risk Assessment , Risk Factors , Time Factors , Treatment Outcome , United Kingdom/epidemiology , Young Adult
13.
Biochemistry ; 54(6): 1380-9, 2015 Feb 17.
Article in English | MEDLINE | ID: mdl-25621740

ABSTRACT

RalA and RalB are members of the Ras family of small G proteins and are activated downstream of Ras via RalGEFs. The RalGEF-Ral axis represents one of the major effector pathways controlled by Ras and as such is an important pharmacological target. RalA and RalB are approximately 80% identical at the amino acid level; despite this, they have distinct roles both in normal cells and in the disease state. We have used our structure of RalB-RLIP76 to guide an analysis of Ral-effector interaction interfaces, creating panels of mutant proteins to probe the energetics of these interactions. The data provide a physical mechanism that underpins the effector selective mutations commonly employed to dissect Ral G protein function. Comparing the energetic landscape of the RalB-RLIP76 and RalB-Sec5 complexes reveals mutations in RalB that lead to differential binding of the two effector proteins. A panel of RLIP76 mutants was used to probe the interaction between RLIP76 and RalA and -B. Despite 100% sequence identity in the RalA and -B contact residues with RLIP76, differences still exist in the energetic profiles of the two complexes. Therefore, we have revealed properties that may account for some of the functional separation observed with RalA and RalB at the cellular level. Our mutations, in both the Ral isoforms and RLIP76, provide new tools that can be employed to parse the complex biology of Ral G protein signaling networks. The combination of these thermodynamic and structural data can also guide efforts to ablate RalA and -B activity with small molecules and peptides.


Subject(s)
Protein Isoforms/chemistry , Thermodynamics , ral GTP-Binding Proteins/chemistry , ATP-Binding Cassette Transporters/chemistry , GTPase-Activating Proteins/chemistry , Vesicular Transport Proteins/chemistry
14.
Structure ; 21(12): 2131-42, 2013 Dec 03.
Article in English | MEDLINE | ID: mdl-24207123

ABSTRACT

RLIP76 is an effector for Ral small GTPases, which in turn lie downstream of the master regulator Ras. Evidence is growing that Ral and RLIP76 play a role in tumorigenesis, invasion, and metastasis. RLIP76 contains both a RhoGAP domain and a Ral binding domain (GBD) and is, therefore, a node between Ras and Rho family signaling. The structure of the RhoGAP-GBD dyad reveals that the RLIP76 RhoGAP domain adopts a canonical RhoGAP domain structure and that the linker between the two RLIP76 domains is structured, fixing the orientation of the two domains and allowing RLIP76 to interact with Rho-family GTPases and Ral simultaneously. However, the juxtaposed domains do not influence each other functionally, suggesting that the RLIP76-Ral interaction controls cellular localization and that the fixed orientation of the two domains orientates the RhoGAP domain with respect to the membrane, allowing it to be perfectly poised to engage its target G proteins.


Subject(s)
ATP-Binding Cassette Transporters/chemistry , Cell Membrane/metabolism , GTP-Binding Proteins/chemistry , GTPase-Activating Proteins/chemistry , ral GTP-Binding Proteins/chemistry , ATP-Binding Cassette Transporters/metabolism , Amino Acid Sequence , GTP-Binding Proteins/metabolism , GTPase-Activating Proteins/metabolism , Humans , Models, Molecular , Molecular Sequence Data , Protein Binding , Protein Structure, Tertiary , cdc42 GTP-Binding Protein/chemistry , rac1 GTP-Binding Protein/chemistry , ral GTP-Binding Proteins/metabolism , ras Proteins/metabolism
15.
BMC Oral Health ; 13: 58, 2013 Oct 26.
Article in English | MEDLINE | ID: mdl-24160246

ABSTRACT

BACKGROUND: Periodontal disease is the most common oral disease affecting adults, and although it is largely preventable it remains the major cause of poor oral health worldwide. Accumulation of microbial dental plaque is the primary aetiological factor for both periodontal disease and caries. Effective self-care (tooth brushing and interdental aids) for plaque control and removal of risk factors such as calculus, which can only be removed by periodontal instrumentation (PI), are considered necessary to prevent and treat periodontal disease thereby maintaining periodontal health. Despite evidence of an association between sustained, good oral hygiene and a low incidence of periodontal disease and caries in adults there is a lack of strong and reliable evidence to inform clinicians of the relative effectiveness (if any) of different types of Oral Hygiene Advice (OHA). The evidence to inform clinicians of the effectiveness and optimal frequency of PI is also mixed. There is therefore an urgent need to assess the relative effectiveness of OHA and PI in a robust, sufficiently powered randomised controlled trial (RCT) in primary dental care. METHODS/DESIGN: This is a 5 year multi-centre, randomised, open trial with blinded outcome evaluation based in dental primary care in Scotland and the North East of England. Practitioners will recruit 1860 adult patients, with periodontal health, gingivitis or moderate periodontitis (Basic Periodontal Examination Score 0-3). Dental practices will be cluster randomised to provide routine OHA or Personalised OHA. To test the effects of PI each individual patient participant will be randomised to one of three groups: no PI, 6 monthly PI (current practice), or 12 monthly PI.Baseline measures and outcome data (during a three year follow-up) will be assessed through clinical examination, patient questionnaires and NHS databases.The primary outcome measures at 3 year follow up are gingival inflammation/bleeding on probing at the gingival margin; oral hygiene self-efficacy and net benefits. DISCUSSION: IQuaD will provide evidence for the most clinically-effective and cost-effective approach to managing periodontal disease in dentate adults in Primary Care. This will support general dental practitioners and patients in treatment decision making. TRIAL REGISTRATION: Protocol ID: ISRCTN56465715.


Subject(s)
Counseling , Dental Care/standards , Oral Hygiene/education , Periodontal Diseases/prevention & control , Primary Health Care/standards , Quality of Health Care , Adult , Aged , Dental Calculus/prevention & control , Dental Care/economics , Dental Plaque/prevention & control , Dental Prophylaxis/economics , Dental Prophylaxis/standards , Follow-Up Studies , Gingival Hemorrhage/prevention & control , Gingivitis/prevention & control , Health Behavior , Health Knowledge, Attitudes, Practice , Humans , Middle Aged , Oral Hygiene/economics , Periodontal Pocket/prevention & control , Periodontitis/prevention & control , Precision Medicine , Quality of Life , Self Care , Self Efficacy , Single-Blind Method , Toothbrushing/methods , Treatment Outcome
16.
Biomol NMR Assign ; 6(2): 119-22, 2012 Oct.
Article in English | MEDLINE | ID: mdl-21915608

ABSTRACT

RLIP76 (also known as RalBP1) is an effector for Ral small G proteins. RLIP76 is a multifunctional, multi-domain protein that includes a GTPase activating domain for the Rho family (RhoGAP domain) and a GTPase binding domain (GBD) for the Ral small G proteins. The juxtaposition of these two domains (GAP and GBD) may be a strategy employed to co-ordinate regulation of Rho family and Ral-controlled signalling pathways at a crossover node. Here we present the (1)H, (15)N and (13)C NMR backbone and sidechain resonance assignments of the GAP and GBD di-domain (31 kDa).


Subject(s)
ATP-Binding Cassette Transporters/chemistry , GTPase-Activating Proteins/chemistry , Nuclear Magnetic Resonance, Biomolecular , Protons , Amino Acid Sequence , Carbon Isotopes , Molecular Sequence Data , Nitrogen Isotopes , Protein Structure, Secondary , Protein Structure, Tertiary
17.
Structure ; 18(8): 985-95, 2010 Aug 11.
Article in English | MEDLINE | ID: mdl-20696399

ABSTRACT

RLIP76 (RalBP1) is a multidomain protein that interacts with multiple small G protein families: Ral via a specific binding domain, and Rho and R-Ras via a GTPase activating domain. RLIP76 interacts with endocytosis proteins and has also been shown to behave as a membrane ATPase that transports chemotherapeutic agents from the cell. We have determined the structure of the Ral-binding domain of RLIP76 and show that it comprises a coiled-coil motif. The structure of the RLIP76-RalB complex reveals a novel mode of binding compared to the structures of RalA complexed with the exocyst components Sec5 and Exo84. RLIP76 interacts with both nucleotide-sensitive regions of RalB, and key residues in the interface have been identified using affinity measurements of RalB mutants. Sec5, Exo84, and RLIP76 bind Ral proteins competitively and with similar affinities in vitro.


Subject(s)
ATP-Binding Cassette Transporters/chemistry , GTPase-Activating Proteins/chemistry , Models, Molecular , Multiprotein Complexes/chemistry , Protein Binding , Protein Conformation , ral GTP-Binding Proteins/chemistry , ATP-Binding Cassette Transporters/metabolism , Amino Acid Sequence , Crystallography, X-Ray , GTPase-Activating Proteins/metabolism , Humans , Molecular Sequence Data , Molecular Structure , Multiprotein Complexes/metabolism , Nuclear Magnetic Resonance, Biomolecular , Scintillation Counting , Sequence Alignment , Vesicular Transport Proteins/metabolism , ral GTP-Binding Proteins/metabolism
19.
FEMS Microbiol Ecol ; 67(3): 381-8, 2009 Mar.
Article in English | MEDLINE | ID: mdl-19187213

ABSTRACT

We tested the hypothesis that different minerals in soil select distinct bacterial communities in their microhabitats. Mica (M), basalt (B) and rock phosphate (RP) were incubated separately in soil planted with Trifolium subterraneum, Lolium rigidum or left unplanted. After 70 days, the mineral and soil fractions were separated by sieving. Automated ribosomal intergenic spacer analysis was used to determine whether the bacterial community structure was affected by the mineral, fraction and plant treatments. Principal coordinate plots showed clustering of bacterial communities from different fraction and mineral treatments, but not from different plant treatments. Permutational multivariate anova (permanova) showed that the microhabitats of M, B and RP selected bacterial communities different from each other in unplanted and L. rigidum, and in T. subterraneum, bacterial communities from M and B differed (P<0.046). permanova also showed that each mineral fraction selected bacterial communities different from the surrounding soil fraction (P<0.05). This study shows that the structure of bacterial communities in soil is influenced by the mineral substrates in their microhabitat and that minerals in soil play a greater role in bacterial ecology than simply providing an inert matrix for bacterial growth. This study suggests that mineral heterogeneity in soil contributes to the spatial variation in bacterial communities.


Subject(s)
Bacteria/growth & development , Ecosystem , Minerals/analysis , Soil Microbiology , Analysis of Variance , Bacteria/genetics , DNA, Bacterial/analysis , DNA, Ribosomal Spacer/analysis , Lolium/growth & development , Trifolium/growth & development
20.
Biochemistry ; 48(10): 2192-206, 2009 Mar 17.
Article in English | MEDLINE | ID: mdl-19166349

ABSTRACT

The small G proteins RalA/B have a crucial function in the regulatory network that couples extracellular signals with appropriate cellular responses. RalA/B are an important component of the Ras signaling pathway and, in addition to their role in membrane trafficking, are implicated in the initiation and maintenance of tumorigenic transformation of human cells. RalA and RalB share 85% sequence identity and collaborate in supporting cancer cell proliferation but have markedly different effects. RalA is important in mediating proliferation, while depletion of RalB results in transformed cells undergoing apoptosis. Crystal structures of RalA in the free form and in complex with its effectors, Sec5 and Exo84, have been solved. Here we have determined the solution structure of free RalB bound to the GTP analogue GMPPNP to an RMSD of 0.6 A. We show that, while the overall architecture of RalB is very similar to the crystal structure of RalA, differences exist in the switch regions, which are sensitive to the bound nucleotide. Backbone 15N dynamics suggest that there are four regions of disorder in RalB: the P-loop, switch I, switch II, and the loop comprising residues 116-121, which has a single residue insertion compared to RalA. 31P NMR data and the structure of RalB.GMPPNP show that the switch regions predominantly adopt state 1 (Ras nomenclature) in the unbound form, which in Ras is not competent to bind effectors. In contrast, 31P NMR analysis of RalB.GTP reveals that conformations corresponding to states 1 and 2 are both sampled in solution and that addition of an effector protein only partially stabilizes state 2.


Subject(s)
Models, Molecular , Vesicular Transport Proteins/chemistry , ral GTP-Binding Proteins/chemistry , Amino Acid Substitution/physiology , Animals , Guanosine Triphosphate/chemistry , Guanylyl Imidodiphosphate/chemistry , Humans , Mice , Nuclear Magnetic Resonance, Biomolecular , Protein Binding , Protein Conformation , Protein Structure, Secondary , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Structural Homology, Protein , Vesicular Transport Proteins/genetics , Vesicular Transport Proteins/metabolism , ral GTP-Binding Proteins/genetics , ral GTP-Binding Proteins/metabolism
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