Hydrogen exchange of disordered proteins in Escherichia coli

A truly disordered protein lacks a stable fold and its backbone amide protons exchange with solvent at rates predicted from studies of unstructured peptides. We have measured the exchange rates of two model disordered proteins, FlgM and α-synuclein, in buffer and in Escherichia coli using the NMR experiment, SOLEXSY. The rates are similar in buffer and cells and are close to the rates predicted from data on small, unstructured peptides. This result indicates that true disorder can persist inside the crowded cellular interior and that weak interactions between proteins and macromolecules in cells do not necessarily affect intrinsic rates of exchange.     

Polar body formation in Spisula oocytes: function of the peripheral aster

Activated Spisula oocytes proceed through meiotic stages rapidly and in near synchrony, providing an excellent system for analyzing polar body formation. Our previous studies suggested that cortical spreading of the metaphase peripheral aster determines spatial features of the cortical F-actin ring that is generated prior to extrusion of the polar body. We tested this hypothesis by experimentally altering the number and cortical contact patterns of peripheral asters. Such alteration was achieved by (a) lovastatin-induced arrest at metaphase I, with and without hexylene glycol modification, followed by washout; and (b) cytochalasin-D inhibition of extrusion of the first polar body, with washout before extrusion of the second polar body. Both methods induced simultaneous formation of two or more cortically spreading asters, correlated with subsequent formation of double, or even triple, overlapping F-actin rings during anaphase. Regardless of pattern, ring F-actin was deposited near regions of greatest astral microtubule density, indicating that microtubules provided a positive stimulus to which the cortex responded indiscriminately. These results strongly support the proposed causal relationship between peripheral aster spreading and biogenesis of the F-actin ring involved in polar body formation.     

Airway cellularity, lipid laden macrophages and microbiology of gastric juice and airways in children with reflux oesophagitis

Background and methods

Human metapneumovirus (hMPV) is a recently discovered respiratory virus associated with bronchiolitis, pneumonia, croup and exacerbations of asthma. Since respiratory viruses are frequently detected in patients with acute exacerbations of COPD (AE-COPD) it was our aim to investigate the frequency of hMPV detection in a prospective cohort of hospitalized patients with AE-COPD compared to patients with stable COPD and to smokers without by means of quantitative real-time RT-PCR.

Results

We analysed nasal lavage and induced sputum of 130 patients with AE-COPD, 65 patients with stable COPD and 34 smokers without COPD. HMPV was detected in 3/130 (2.3%) AE-COPD patients with a mean of 6.5 × 10⁵ viral copies/ml in nasal lavage and 1.88 × 10⁵ viral copies/ml in induced sputum. It was not found in patients with stable COPD or smokers without COPD.

Conclusion

HMPV is only found in a very small number of patients with AE-COPD. However it should be considered as a further possible viral trigger of AE-COPD because asymptomatic carriage is unlikely.     

Formation and function of the polar body contractile ring in Spisula

Initial studies suggested that spatial organization of the putative polar body contractile ring was determined by the peripheral aster in Spisula [Biol. Bull. 205 (2003) 192]. Here we report detailed supporting observations, including testing of aster and ring function with inhibitors. The metaphase peripheral aster was confirmed to spread cortically in an umbrella-like pattern, with microtubule-poor center. The aster disassembled during anaphase, leaving the spindle docked at the F-actin-poor center of a newly generated cortical F-actin ring that closely approximated the aster in location, measured diameter range, and pattern. Cytochalasin D and latrunculin-B permitted all events except ring and polar body formation. Nocodazole disassembly or taxol stabilization of the peripheral aster produced poorly defined rings or bulging anaphase asters within the ring center, respectively, inhibiting polar body formation. Polar body extrusion occurred at the ring center, the diameter of which diminished. Ring contractility-previously assumed-was verified using blebbistatin, a myosin-II ATPase inhibitor that permitted ring assembly but blocked polar body extrusion. The data support the hypothesis that peripheral aster spreading, perhaps dynein-driven, is causally related to polar body contractile ring formation, with anaphase entry and aster disassembly also required for polar body biogenesis. Previously reported astral spreading during embryonic micromere formation suggests that related mechanisms are involved in asymmetric somatic cytokinesis.     

Cytomegalovirus seropositivity is associated with glucose regulation in the oldest old. Results from the Leiden 85-plus Study

ABSTRACT: BACKGROUND: Cytomegalovirus (CMV) infection has been reported to contribute to the pathogenesis of type 1 diabetes and post-transplantation diabetes. However, CMV infection has not been evaluated as a possible risk factor for type 2 diabetes. Our aim was to investigate potential associations between CMV seropositivity, CMV IgG antibody level and glucose regulation in the oldest old. RESULTS: CMV seropositive subjects were more likely to have type 2 diabetes (17.2% vs 7.9%, p = 0.016), had a higher level of HbA1c (p = 0.014) and higher non-fasting glucose (p = 0.024) in the oldest olds. These associations remained significant after adjustment for possible confounders. CMV IgG antibody level was not significantly associated with glucose regulation (all p > 0.05). CONCLUSIONS: In the oldest old, CMV seropositivity is significantly associated with various indicators of glucose regulation. This finding suggests that CMV infection might be a risk factor for the development of type 2 diabetes in the elderly.     

Partially formed native tertiary interactions in the A-state of cytochrome c.

Considerable insight into protein structure, stability, and folding has been obtained from studies of non-native states. We have studied the extent of native tertiary contacts in one such molecule, the A-state of yeast iso-1-ferricytochrome c. Previously, we showed that the interface between the N and C-terminal helices is completely formed in the A-state. Here, we focus on interactions essential for forming the heme pocket of eukaryotic cytochromes c. To determine the extent of these interactions, we used saturation mutagenesis at the evolutionarily invariant residue leucine 68, and measured the free energy of denaturation for the native states and the A-states of functional variants. We show that, unlike the interaction between the terminal helices, the native interactions between the 60s helix and the rest of the protein are not completely formed in the A-state.     

Natriuretic peptides modify <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis> cytotoxicity by regulating cyclic nucleotides and modifying LPS structure

Background  

Nervous tissues express various communication molecules including natriuretic peptides, i.e. Brain Natriuretic Peptide (BNP) and C-type Natriuretic Peptide (CNP). These molecules share structural similarities with cyclic antibacterial peptides. CNP and to a lesser extent BNP can modify the cytotoxicity of the opportunistic pathogen Pseudomonas aeruginosa. The psychrotrophic environmental species Pseudomonas fluorescens also binds to and kills neurons and glial cells, cell types that both produce natriuretic peptides. In the present study, we investigated the sensitivity of Pseudomonas fluorescens to natriuretic peptides and evaluated the distribution and variability of putative natriuretic peptide-dependent sensor systems in the Pseudomonas genus.     

Involvement of a phospholipase C in the hemolytic activity of a clinical strain of <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis>

Background  

Pseudomonas fluorescens is a ubiquitous Gram-negative bacterium frequently encountered in hospitals as a contaminant of injectable material and surfaces. This psychrotrophic bacterium, commonly described as unable to grow at temperatures above 32°C, is now considered non pathogenic. We studied a recently identified clinical strain of P. fluorescens biovar I, MFN1032, which is considered to cause human lung infection and can grow at 37°C in laboratory conditions.     

Colonisation and mass rearing: learning from others

Mosquitoes, just as other insects produced for the sterile insect technique (SIT), are subjected to several unnatural processes including laboratory colonisation and large-scale factory production. After these processes, sterile male mosquitoes must perform the natural task of locating and mating with wild females. Therefore, the colonisation and production processes must preserve characters necessary for these functions. Fortunately, in contrast to natural selection which favours a suite of characteristics that improve overall fitness, colonisation and production practices for SIT strive to maximize only the few qualities that are necessary to effectively control populations.However, there is considerable uncertainty about some of the appropriate characteristics due to the lack of data. Development of biological products for other applications suggest that it is possible to identify and modify competitiveness characteristics in order to produce competitive mass produced sterile mosquitoes. This goal has been pursued - and sometimes achieved - by mosquito colonisation, production, and studies that have linked these characteristics to field performance. Parallels are drawn to studies in other insect SIT programmes and aquaculture which serve as vital technical reference points for mass-production of mosquitoes, most of whose development occurs - and characteristics of which are determined - in an aquatic environment. Poorly understood areas that require further study are numerous: diet, mass handling and genetic and physiological factors that influence mating competitiveness. Compromises in such traits due to demands to increase numbers or reduce costs, should be carefully considered in light of the desired field performance.     

Temperature-induced reversible conformational change in the first 100 residues of alpha-synuclein

Natively disordered proteins are a growing class of anomalies to the structure-function paradigm. The natively disordered protein alpha-synuclein is the primary component of Lewy bodies, the cellular hallmark of Parkinson's disease. We noticed a dramatic difference in dilute solution 1H-15N Heteronuclear Single Quantum Coherence (HSQC) spectra of wild-type alpha-synuclein and two disease-related mutants (A30P and A53T), with spectra collected at 35 degrees C showing fewer cross-peaks than spectra acquired at 10 degrees C. Here, we show the change to be the result of a reversible conformational exchange linked to an increase in hydrodynamic radius and secondary structure as the temperature is raised. Combined with analytical ultracentrifugation data showing alpha-synuclein to be monomeric at both temperatures, we conclude that the poor quality of the 1H-15N HSQC spectra obtained at 35 degrees C is due to conformational fluctuations that occur on the proton chemical shift time scale. Using a truncated variant of alpha-synuclein, we show the conformational exchange occurs in the first 100 amino acids of the protein. Our data illustrate a key difference between globular and natively disordered proteins. The properties of globular proteins change little with solution conditions until they denature cooperatively, but the properties of natively disordered proteins can vary dramatically with solution conditions.