Effect of obesity on aromatase inhibitor efficacy in postmenopausal, hormone receptor-positive breast cancer: a systematic review.

Aromatase inhibitors (AIs) decrease the production of oestrogen, decreasing stimulation of hormone receptor-positive breast cancer. Theoretically, AIs may be less effective in obese women, due to the greater quantity of aromatase in peripheral fatty tissue. We performed a systematic review to assess the effect of obesity on AI efficacy in breast cancer treatment. The review followed PRISMA guidelines. Studies included were interventional or observational studies with comparison groups, of postmenopausal women with hormone receptor-positive breast cancer on treatment with an AI, alone or in combination with other drugs, in which body mass index or another measure of obesity was recorded. Studies in all languages were included; if published as an abstract only, authors were contacted for further information. Outcome measures included overall survival, disease-free survival or time to progressive disease, survival from the start of therapy, mortality measures, local or distant recurrence of primary cancer and time to recurrence. Of 2,344 citations identified from five databases, eight studies met the criteria for inclusion; three randomised controlled trials and five retrospective cohort studies. Due to variability in study factors, it was not possible to perform a quantitative meta-analysis. However, the systematic review showed a trend towards a negative effect of obesity on AI efficacy. There is evidence of a negative effect of obesity on AI efficacy in postmenopausal hormone receptor-positive breast cancer, but the size of the effect cannot be assessed. More information is needed before clinical recommendations are made.

Adverse obstetrical outcomes after treatment of precancerous cervical lesions: a Belgian multicentre study.

OBJECTIVE: To assess the impact of cervical intraepithelial neoplasia (CIN) treatment on the risk of (spontaneous) preterm delivery (PD) and small for gestational age (SGA) at birth. DESIGN: A multicentre cohort study. SETTING: Maternity wards of four academic hospitals in Belgium. POPULATION: Ninety-seven exposed pregnant women (with a CIN treatment history) and 194 nonexposed pregnant women (without a history of CIN treatment). METHODS: A questionnaire and check of obstetrical files included socio-demographic characteristics, risk factors for PD, obstetrical history for all women and characteristics of the CIN treatment for exposed women. Pregnancy outcomes were recorded after delivery. The influence of previous treatment of CIN on pregnancy outcomes, adjusted for confounding variables, was assessed by Cox regression and lifetables (for the outcome gestational age at birth) and by logistic regression (for the outcomes PD and SGA at birth). MAIN OUTCOME MEASURES: Occurrence of PD and SGA at birth. RESULTS: Seventy-nine per cent of the women in the database were multiparous; 16.3% of women with a previous excisional treatment spontaneously delivered preterm, compared with 8.1% of unexposed women [odds ratio (OR), 2.19; 95% confidence interval (CI), 0.97-4.99]. When adjusting for confounding factors (ethnicity, HIV status, education, age, smoking and parity), the OR for PD was 2.33 (95% CI, 0.99-5.49). Excisional treatment did not have an impact on SGA at birth (OR, 0.94; 95% CI,0.41-2.15). The depth of the cone was >10 mm in 63.5% of the documented cases. Large cones, more than 10 mm deep, were associated with a significantly increased risk of PD (adjusted OR, 4.55; 95% CI, 1.32-15.65) compared with untreated women, whereas smaller cones (≤ 10 mm) were not significantly associated with PD (OR, 2.77; 95% CI, 0.28-27.59). The associations seen for PD with respect to the cone size did not hold for SGA at birth. CONCLUSIONS: There was an increased risk of (spontaneous) PD after excision of CIN, in particular when the cone depth exceeded 10 mm.

Neoliberal discourse, actor power, and the politics of nutrition policy: A qualitative analysis of informal challenges to nutrition labelling regulations at the World Trade Organization, 2007-2019.

Unhealthy diets are increasing contributors to poor health and mortality in low- and middle-income countries (LMICs). Government interventions targeting the structural drivers of unhealthy diets are needed to prevent these illnesses, including nutrition labelling regulations that create healthier food environments. Yet, implementation remains slow and uneven. One explanation for slow implementation highlights the role of politics, including powerful ideological discourse and its strategic deployment by economically powerful actors. In this article, we advance research on the politics of nutrition policies by analysing political discourse on nutrition labelling regulations within an influential and under-studied global institution: the World Trade Organization (WTO). We identified WTO Technical Barriers to Trade (TBT) Committee meeting minutes with reference to nutrition labelling policies proposed by Thailand, Chile, Indonesia, Peru, Ecuador, Bolivia, and Uruguay (2007-2019; n = 47). We analysed the frames, narratives, and normative claims that feature in inter-country discourse within TBT meetings and examined how actors mobilize ideological and material sources of power via these statements. We find that informal government challenges to nutrition labelling proposals within the Committee featured a narrative that individualized the causes of and solutions to poor diet, downplayed harms from industrialised food products, and framed state regulation as harmful and unjust. These non-technical claims mobilised neoliberal ideology and rhetoric to contest the normative legitimacy of members' proposals and to de-socialize and de-politicize poor diets. Furthermore, high-income countries (HICs) re-framed policy goals to focus on individual determinants of poor nutrition whilst calling for their preferred policies to be adopted. Patterns of discourse within TBT meetings also had striking similarities with arguments raised by multi-national food corporations elsewhere. Our findings suggest that non-technical and ideological arguments raised during TBT meetings serve as inconspicuous tools through which nutrition labelling policies in LMICs are undermined by HICs, industry, and the powerful ideology of neoliberalism.

Globalization and health policy space: Introducing the WTOhealth dataset of trade challenges to national health regulations at World Trade Organization, 1995-2016.

Do international trade rules and agreements constrain health policy space? A multitude of global actors and institutions with different interests and power can shape national health policy, and trade rules provide one means through which to exert pressure on governments. Yet, the full scope of political pressure on health policy within the global trade regime is insufficiently understood, as previous research largely focussed on challenges to food, alcohol, and tobacco regulations and used small-N case studies. This potentially overlooks other domains of influence and we lack an understanding of quantitative trends and patterns therein. In this article we introduce a novel dataset, WTOhealth, comprising all challenges to national health regulations at the WTO Technical Barriers to Trade (TBT) Committee between 1995 and 2016. The dataset is based on 1496 pages of minutes from 71 TBT meetings. We describe how we developed this dataset and present an exploratory analysis of key patterns within the data. Our analysis shows that WTO members raised 250 trade challenges to health regulations between 1995 and 2016. 83.6% of challenges to low- or lower-middle income country (LMIC) members were raised by high-income countries (HICs). Many challenges centred on food (16.4% challenges), alcohol (10.4%), and tobacco (4.2%) policies, but a substantial proportion concerned other products, including toxic chemicals (9.1%), pharmaceuticals and medical devices (8.1%), machinery (7.8%), and motor vehicles (7.3%). This includes measures targeting medical device safety, increased access to pharmaceuticals, and reduced exposure to toxins harmful to both health and the environment. We further examine these challenges, finding that HIC members made claims with contentious scientific support. In short, diverse health regulations may be changed or delayed following contentious challenges at the TBT Committee. There is a need for further research investigating the nature and influence of WTO challenges to diverse health regulations.

A case of pilomyxoid astrocytoma presenting with CSF rhinorrhoea in a 15-year-old.

We report a pilomyxoid astrocytoma (PMA) presenting with CSF rhinorrhoea in a 15-year-old. This uncommon, recently described entity typically presents in infancy with focal neurological or endocrine symptoms, has distinctive histologic features and displays a more aggressive behaviour than pilocytic astrocytoma (PA) with which it was previously classified.

[Major alpha-thalassemia: antenatal diagnosis, case report and literature review]. / Alpha-thalassémie majeure: à propos d'un cas de dépistage anténatal et revue de la littérature.

Homozygous alpha-thalassaemia or Bart's hydrops fetalis is a genetic disease with autosomal recessive transmission. The condition is lethal for the fetus because of hypoxia and anemia. For the mother there is an increased risk of the severe forms of preeclampsia and its complications. The diagnosis can be suspected in presence of suggestive ultrasonographic anomalies, where both parents come from South-East Asia or China. Confirmation is based on the identification of the typical deletions or mutation of the alpha globin gene by molecular genetics. We report a rare clinical case of Bart's hydrops fetalis diagnosed because of fetal growth retardation, fetal cardiomegaly and increased size of placenta on the 26 weeks fetal echography. This case underscores the need to include the alpha thalassemias in medical and midwifery education in countries where they were almost inexistent a generation ago.

Assessment and validation of a screening questionnaire for the diagnosis of pediatric bladder and bowel dysfunction.

INTRODUCTION: Pediatric bladder and bowel dysfunction (BBD) is a common problem in children. However, the current ability to diagnosis and quantify pediatric BBD is limited as only a few validated instruments exist. In addition, the current questionnaires are limited by their lack of psychometric processing and methods of validation. To address these issues, the authors developed a new questionnaire to objectively diagnose pediatric BBD symptoms. This study aimed to evaluate the performance of this newly devised objective instrument in diagnosing and quantifying the symptomatology of BBD in children. MATERIALS AND METHODS: An 18-item, 5-point questionnaire was developed using both a literature review and expert opinions. The total questionnaire score could range from 0 to 72. Questions were subgrouped into six symptom categories: (1) nocturnal enuresis, (2) lower urinary tract symptoms, (3) urinary holding, (4) infrequent urination, (5) bowel symptoms, and (6) daytime urinary incontinence. The questionnaire also assessed the degree of bother associated with the symptoms. Patients were divided into cases and controls, and these two groups were compared. DISCUSSION/RESULTS: A total of 1265 new patients (758 cases and 507 controls) completed the new BBD questionnaire. The mean age of the whole study cohort was 9.5 years (range, 3-19 years). The total mean questionnaire score was significantly higher at 23 (3-58) in the cases, compared with 8 (0-35) in the controls (p < 0.001) (Summary Figure). Reliability analysis of the 18-item instrument showed a Cronbach's alpha reliability coefficient of 0.80 for the scale. CONCLUSIONS: This new instrument provides a valid and reliable method for diagnosis of pediatric BBD and classification of patients into subcategories of BBD based on their specific symptoms.

Translational mini-review series on complement factor H: structural and functional correlations for factor H.

The 155-kDa glycoprotein, complement factor H (CFH), is a regulator of complement activation that is abundant in human plasma. Three-dimensional structures of over half the 20 complement control protein (CCP) modules in CFH have been solved in the context of single-, double- and triple-module segments. Proven binding sites for C3b occupy the N and C termini of this elongated molecule and may be brought together by a bend in CFH mediated by its central CCP modules. The C-terminal CCP 20 is key to the ability of the molecule to adhere to polyanionic markers on self-surfaces where CFH acts to regulate amplification of the alternative pathway of complement. The surface patch on CCP 20 that binds to model glycosaminoglycans has been mapped using nuclear magnetic resonance (NMR), as has a second glycosaminoglycan-binding patch on CCP 7. These patches include many of the residue positions at which sequence variations have been linked to three complement-mediated disorders: dense deposit disease, age-related macular degeneration and atypical haemolytic uraemic syndrome. In one plausible model, CCP 20 anchors CFH to self-surfaces via a C3b/polyanion composite binding site, CCP 7 acts as a 'proof-reader' to help discriminate self- from non-self patterns of sulphation, and CCPs 1-4 disrupt C3/C5 convertase formation and stability.

Hepatitis B or hepatitis C coinfection in HIV-infected pregnant women in Europe.

OBJECTIVES: The aim of the study was to investigate the prevalence of and risk factors for hepatitis C or B virus (HCV or HBV) coinfection among HIV-infected pregnant women, and to investigate their immunological and virological characteristics and antiretroviral therapy use. METHODS: Information on HBV surface antigen (HBsAg) positivity and HCV antibody (anti-HCV) was collected retrospectively from the antenatal records of HIV-infected women enrolled in the European Collaborative Study and linked to prospectively collected data. RESULTS: Of 1050 women, 4.9% [95% confidence interval (CI) 3.6-6.3] were HBsAg positive and 12.3% (95% CI 10.4-14.4) had anti-HCV antibody. Women with an injecting drug use(r) (IDU) history had the highest HCV-seropositivity prevalence (28%; 95% CI 22.8-35.7). Risk factors for HCV seropositivity included IDU history [adjusted odds ratio (AOR) 2.92; 95% CI 1.86-4.58], age (for > or =35 years vs. <25 years, AOR 3.45; 95% CI 1.66-7.20) and HBsAg carriage (AOR 5.80; 95% CI 2.78-12.1). HBsAg positivity was associated with African origin (AOR 2.74; 95% CI 1.20-6.26) and HCV seropositivity (AOR 6.44; 95% CI 3.08-13.5). Highly active antiretroviral therapy (HAART) use was less likely in HIV/HCV-seropositive than in HIV-monoinfected women (AOR 0.34; 95% CI 0.20-0.58). HCV seropositivity was associated with a higher adjusted HIV RNA level (+0.28 log(10) HIV-1 RNA copies/mL vs. HIV-monoinfected women; P=0.03). HIV/HCV-seropositive women were twice as likely to have detectable HIV in the third trimester/delivery as HIV-monoinfected women (AOR 1.95; P=0.049). CONCLUSIONS: Although HCV serostatus impacted on HAART use, the association between HCV seropositivity and uncontrolled HIV viraemia in late pregnancy was independent of HAART.

The effect of lunisolar tidal acceleration on stem elongation growth, nutations and leaf movements in peppermint (Mentha × piperita L.).

Orbital movement of the Moon generates a system of gravitational fields that periodically alter the gravitational force on Earth. This lunar tidal acceleration (Etide) is known to act as an external environmental factor affecting many growth and developmental phenomena in plants. Our study focused on the lunar tidal influence on stem elongation growth, nutations and leaf movements of peppermint. Plants were continuously recorded with time-lapse photography under constant illumination as well in constant illumination following 5 days of alternating dark-light cycles. Time courses of shoot movements were correlated with contemporaneous time courses of the Etide estimates. Optical microscopy and SEM were used in anatomical studies. All plant shoot movements were synchronised with changes in the lunisolar acceleration. Using a periodogram, wavelet analysis and local correlation index, a convergence was found between the rhythms of lunisolar acceleration and the rhythms of shoot growth. Also observed were cyclical changes in the direction of rotation of stem apices when gravitational dynamics were at their greatest. After contrasting dark-light cycle experiments, nutational rhythms converged to an identical phase relationship with the Etide and almost immediately their renewed movements commenced. Amplitudes of leaf movements decreased during leaf growth up to the stage when the leaf was fully developed; the periodicity of leaf movements correlated with the Etide rhythms. For the fist time, it was documented that lunisolar acceleration is an independent rhythmic environmental signal capable of influencing the dynamics of plant stem elongation. This phenomenon is synchronised with the known effects of Etide on nutations and leaf movements.

Motile plant cell body: a "bug" within a "cage".

Analysis of the cytoskeleton in morphogenetically active plant cells allows us to propose a unified concept for the structural organization of eukaryotic cells. Their cytoarchitecture is determined by two principal structural complexes: nucleus-microtubule-based cell bodies ("bugs") and plasma-membrane-F-actin-based cell periphery complexes ("cages"). There are dynamic interactions between each of these entities in response to extracellular and intracellular signals. In the case of the cell body, these signals determine its polarization, rotation and migration. Interactions between cell body and cell periphery complexes determine cell growth polarity and morphogenesis throughout the eukaryotic kingdom.

Estimated aortic stiffness is independently associated with cardiac baroreflex sensitivity in humans: role of ageing and habitual endurance exercise.

We hypothesised that differences in cardiac baroreflex sensitivity (BRS) would be independently associated with aortic stiffness and augmentation index (AI), clinical biomarkers of cardiovascular disease risk, among young sedentary and middle-aged/older sedentary and endurance-trained adults. A total of 36 healthy middle-aged/older (age 55-76 years, n=22 sedentary and n=14 endurance-trained) and 5 young sedentary (age 18-31 years) adults were included in a cross-sectional study. A subset of the middle-aged/older sedentary adults (n=12) completed an 8-week-aerobic exercise intervention. Invasive brachial artery blood pressure waveforms were used to compute spontaneous cardiac BRS (via sequence technique), estimated aortic pulse wave velocity (PWV) and AI (AI, via brachial-aortic transfer function and wave separation analysis). In the cross-sectional study, cardiac BRS was 71% lower in older compared with young sedentary adults (P<0.05), but only 40% lower in older adults who performed habitual endurance exercise (P=0.03). In a regression model that included age, sex, resting heart rate, mean arterial pressure (MAP), body mass index and maximal exercise oxygen uptake, estimated aortic PWV (ß±s.e.=-5.76±2.01, P=0.01) was the strongest predictor of BRS (model R(2)=0.59, P<0.001). The 8-week-exercise intervention improved BRS by 38% (P=0.04) and this change in BRS was associated with improved aortic PWV (r=-0.65, P=0.044, adjusted for changes in MAP). Age- and endurance-exercise-related differences in cardiac BRS are independently associated with corresponding alterations in aortic PWV among healthy adults, consistent with a mechanistic link between variations in the sensitivity of the baroreflex and aortic stiffness with age and exercise.

Nuclear components with microtubule-organizing properties in multicellular eukaryotes: functional and evolutionary considerations.

The nucleus and the microtubular cytoskeleton of eukaryotic cells appear to be structurally and functionally interrelated. Together they constitute a "cell body". One of the most important components of this body is a primary microtubule-organizing center (MTOC-I) located on or near the nuclear surface and composed of material that, in addition to constitutive centrosomal material, also comprises some nuclear matrix components. The MTOC-I shares a continuity with the mitotic spindle and, in animal cells, with the centrosome also. Secondary microtubule-organizing centers (MTOC-IIs) are a special feature of walled plant cells and are found at the plasma membrane where they organize arrays of cortical MTs that are essential for ordered cell wall synthesis and hence for cellular morphogenesis. MTOC-IIs are held to be similar in origin to the MTOC-I, but their material has been translocated to the cell periphery, perhaps by MTs organized and radiating from the MTOC-I. Many intranuclear, matrix-related components have been identified to participate in MT organization during mitosis and cytokinesis; some of them also seem to be related to the condensation and decondensation of chromatin during the mitotic chromosome cycle.

Structure of the C3HC4 domain by 1H-nuclear magnetic resonance spectroscopy. A new structural class of zinc-finger.

A recently identified sequence motif, referred to as "C3HC4" (also "RING finger" and "A Box") for its distinctive pattern of putative metal-binding residues, has been found in a wide range of proteins. In a previous paper we described the expression and purification of fragments encompassing this motif from the Vmw110 (IPC0) protein family. We showed that the equine herpes virus protein binds zinc ions and adopts a beta beta alpha beta fold. We now report the tertiary structure of this domain in solution, as determined by two-dimensional 1H-NMR An amphipathic alpha-helix lies along one surface of a triple-stranded beta-sheet. Four pairs of metal-binding residues sequester two zincs at distinct tetrahedral sites. The first and third pairs bind one metal ion, while the second and fourth pairs bind the other, forming an interleaved whole. The first and the fourth pairs are contained within two prominent, well-defined loops related by an approximate dyad symmetry. Conserved residues within the helix, sheet and loops contribute to a compact hydrophobic core. The region comprising the first two beta-strands and the alpha-helix has remarkable structural similarity with a TFIIIA type of zinc finger, even though the C3HC4 domain appears not to bind specifically to DNA or RNA. Using site-directed mutagenesis we demonstrate that exposed polar side-chains of the C3HC4 alpha-helix are essential for trans-activation of gene expression by an intact herpes virus regulatory protein.

A novel arrangement of zinc-binding residues and secondary structure in the C3HC4 motif of an alpha herpes virus protein family.

A highly conserved, cysteine-rich region plays a crucial role in the function of a family of regulatory proteins encoded by alpha herpes viruses. The so-called C3HC4 motif spans approximately 60 residues and has been predicted to bind zinc. This motif occurs in a number of other viral and cellular proteins, many of which appear to be involved in some aspect of the regulation of gene expression. We have cloned and expressed in bacteria a portion of immediate-early protein Vmw110 of herpes simplex virus type 1 that encompasses the C3HC4 motif, and the equivalent regions from the homologous proteins of varicella zoster virus and equine herpes virus type 1 (EHV-1). All three polypeptides were purified and found to bind zinc stably. None of the three interacted significantly with either DNA or RNA under our assay conditions. The EHV-1 domain yielded interpretable proton nuclear magnetic resonance spectra. Assignment of resonances and analysis of nuclear Overhauser effects revealed its secondary structure. Starting from the N terminus, this consists of an ordered but irregular loop, the first two strands of a triple-stranded antiparallel beta-sheet, two turns of an alpha-helix, a second irregular loop, and the third strand of the beta-sheet. It appears that, taking the cysteine and histidine residues in turn, cysteine residues I, II, IV and V co-ordinate one zinc atom while the histidine residue and cysteine residues III, VI and VII co-ordinate a second zinc atom. This arrangement of secondary structure differs from that found in other characterized zinc-containing proteins.

Three-dimensional structure of a complement control protein module in solution.

The complement control protein (CCP) modules (also known as short consensus repeats) are defined by a consensus sequence within a stretch of about 60 amino acid residues. These modules have been identified more than 140 times in over 20 proteins, including 12 proteins of the complement system. The solution structure of the 16th CCP module from human complement factor H has been determined by a combination of 2-dimensional nuclear magnetic resonance spectroscopy and restrained simulated annealing. In all, 548 structurally important nuclear Overhauser enhancement cross-peaks were quantified as distance restraints and, together with 41 experimentally measured angle restraints, were incorporated into a simulated annealing protocol to determine a family of closely related structures that satisfied the experimental observations. The CCP structure is shown to be based on a beta-sandwich arrangement; one face made up of three beta-strands hydrogen-bonded to form a triple-stranded region at its centre and the other face formed from two separate beta-strands. Both faces of the molecule contribute highly conserved hydrophobic side-chains to a compact core. The regions between the beta-strands are composed of both well-defined turns and less well-defined loops. Analysis of CCP sequence alignments, in light of the determined structure, reveals a high degree of conservation amongst residues of obvious structural importance, while almost all insertions, deletions or replacements observed in the known sequences are found in the less well-defined loop regions. On the basis of these observations it is postulated that models of other CCP modules that are based on the structure presented here will be accurate. Certain families of CCP modules differ from the consensus in that they contain extra cysteine residues. As a test of structural consensus, the extra disulphide bridges are shown to be easily accommodated within the determined CCP model.

NMR studies of a viral protein that mimics the regulators of complement activation.

Vaccinia virus complement control protein (VCP) is a 243-residue protein that is similar in sequence to the regulators of complement activation; its role is to defend the virus against attack by the host complement system. A fragment of this protein spanning the two complement protein (CP)-modules (residues 126 to 243) which make up the C-terminal half of VCP has been expressed in Pichia pastoris. A 15N-labelled sample was purified for the purposes of structure determination and measurements of dynamics in solution using NMR. Structures were calculated on the basis of 1767 NMR-derived distance and angle restraints, with a longer than normal high-temperature simulated annealing (SA) protocol which improved convergence. The viral CP-modules are structurally very similar to the 15th and 16th CP-modules of human factor H (fH; average r.m.s.d., for invariant Trp and Cys, four pair-wise comparisons,=1.2 A) but less similar to the fifth CP-module of fH (average r.m.s.d.=2.2 A). In the VCP fragment, the orientation of one module with respect to the other is clearly defined by the experimental data, and T1 measurements are consistent with only limited flexibility at the module-module interface. The r.m.s.d. over all of the 118 residues (backbone atoms) is 0.73 A. The intermodular orientation is better defined than, and significantly different from, that observed in a CP-module pair from fH (re-calculated using the extended SA protocol). In VCP the long axis of the second module is tilted by 59(+/-4) degrees with respect to the first module (50(+/-13) degrees in the fH pair), and twisted with respect to the first module by 22(+/-6) degrees (223(+/-17) degrees in fH). The differences between the human and viral proteins may be rationalised in terms of the lack of hydrogen-bond stabilised secondary structure in the N-terminal portion of fH module 16, and the number and type of amino acid side-chains which make up the interface. A similar intermodular interface may be predicted between the third and fourth module of human C4 binding protein and, probably, between the third and fourth modules of the guinea pig acrosomal matrix protein 67; but the formulation of general rules for predicting the structure of interfaces between CP-modules awaits further experimental data.

Solution structure and dynamics of an open beta-sheet, glycolytic enzyme, monomeric 23.7 kDa phosphoglycerate mutase from Schizosaccharomyces pombe.

The structure and backbone dynamics of a double labelled (15N,13C) monomeric, 23.7 kD phosphoglycerate mutase (PGAM) from Schizosaccharomyces pombe have been investigated in solution using NMR spectroscopy. A set of 3125 NOE-derived distance restraints, 148 restraints representing inferred hydrogen bonds and 149 values of (3)J(HNHalpha) were used in the structure calculation. The mean rmsd from the average structure for all backbone atoms from residues 6-205 in the best 21 calculated structures was 0.59 A. The core of the enzyme includes an open, twisted, six-stranded beta-sheet flanked by four alpha-helices and a short 3(10)-helix. An additional smaller domain contains two short antiparallel beta-strands and a further pair of alpha-helices. The C(alpha) atoms of the S. pombe PGAM may be superimposed on their equivalents in one of the four identical subunits of Saccharomyces cerevisiae PGAM with an rmsd of 1.34 A (0.92 A if only the beta-sheet is considered). Small differences between the two structures are attributable partly to the deletion in the S. pombe sequence of a 25 residue loop involved in stabilising the S. cerevisiae tetramer. Analysis of 15N relaxation parameters indicates that PGAM tumbles isotropically with a rotational correlation time of 8.7 ns and displays a range of dynamic features. Of 178 residues analysed, only 77 could be fitted without invoking terms for fast internal motion or chemical exchange, and out of the remainder, 77 required a chemical exchange term. Significantly, 46 of the slowly exchanging (milli- to microsecond) residues lie in helices, and these account for two-thirds of all analysed helix residues. On the contrary, only one beta-sheet residue required an exchange term. In contrast to other analyses of backbone dynamics reported previously, residues in slow exchange appeared to correlate with architectural features of the enzyme rather than congregating close to ligand binding sites.

Solution structure and dynamics of the central CCP module pair of a poxvirus complement control protein.

The complement control protein (CCP) module (also known as SCR, CCP or sushi domain) is prevalent amongst proteins that regulate complement activation. Functional and mutagenesis studies have shown that in most cases two or more neighbouring CCP modules form specific binding sites for other molecules. Hence the orientation in space of a CCP module with respect to its neighbours and the flexibility of the intermodular junction are likely to be critical for function. Vaccinia virus complement control protein (VCP) is a complement regulatory protein composed of four tandemly arranged CCP modules. The solution structure of the carboxy-terminal half of this protein (CCP modules 3 and 4) has been solved previously. The structure of the central portion (modules 2 and 3, VCP approximately 2,3) has now also been solved using NMR spectroscopy at 37 degrees C. In addition, the backbone dynamics of VCP approximately 2,3 have been characterised by analysis of its (15)N relaxation parameters. Module 2 has a typical CCP module structure while module 3 in the context of VCP approximately 2,3 has some modest but significant differences in structure and dynamics to module 3 within the 3,4 pair. Modules 2 and 3 do not share an extensive interface, unlike modules 3 and 4. Only two possible NOEs were identified between the bodies of the modules, but a total of 40 NOEs between the short intermodular linker of VCP approximately 2,3 and the bodies of the two modules determines a preferred, elongated, orientation of the two modules in the calculated structures. The anisotropy of rotational diffusion has been characterised from (15)N relaxation data, and this indicates that the time-averaged structure is more compact than suggested by (1)H-(1)H NOEs. The data are consistent with the presence of many intermodular orientations, some of which are kinked, undergoing interconversion on a 10(-8)-10(-6) second time-scale. A reconstructed representation of modules 2-4 allows visualisation of the spatial arrangement of the 11 substitutions that occur in the more potent complement inhibitor from Variola (small pox) virus.

Solution structure of a pair of complement modules by nuclear magnetic resonance.

A portion of human complement factor H spanning the 15th (H15) and 16th (H16) of its 20 modules, has been expressed in a yeast vector and subjected to structure determination in solution using two-dimensional 1H-NMR. The structure of H15 is very similar to that already established for the fifth module of factor H and H16, consistent with the view that all such complement control (C-) modules share a common overall topology. In addition, the tertiary structures of the component modules of the H15-16 pair are very similar to those of the modules when expressed individually, implying that each folds entirely autonomously within intact factor H. Aromatic residues in the third turn of H15 and the second turn of H16, together with a leucine residue from the linker region, contribute to a small intermodular interface. Comparatively few nuclear Overhauser effects were observable between protons on different modules. Consequently, a wide range of angles of "twist" (131 (+/- 146) degrees, mean value (+/- 1 standard deviation)), i.e. rotation about the long axis of one module with respect to the other, exists in the family of structures generated on the basis of the experimental data. However, much smaller variations occur in the two, orthogonal, angles (175 (+/- 12) degrees and 103 (+/- 6) degrees) that describe the "tilt". These observations may suggest upper limits on the relative flexibility of the two modules. Models were built to assess the outcome of applying such restrictions to all the neighbours within a string of 20 C-modules, and the resulting structures compare well with factor H as visualized by electron microscopy.