Activation of 11R-lipoxygenase is fully Ca(2+)-dependent and controlled by the phospholipid composition of the target membrane

Activation of some lipoxygenases (LOX) is found to be related to the selective membrane binding upon cell stimulation. In this study, a systematic analysis of the effect of the lipid composition on the membrane binding efficiency, Ca(2+) affinity, and enzymatic activity of 11R-LOX was performed. The analysis of the membrane targeting by fluorometric and surface plasmon resonance measurements in the absence of Ca(2+) showed an exclusive binding of 11R-LOX to the anionic phospholipids (phosphatidylinositol < phosphatidylglycerol ≈ phosphatidylserine) containing model membranes. The presence of Ca(2+) enhanced the rate of interaction and influenced its mode. The modulation of the activity of 11R-LOX indicated that (i) Ca(2+) binding is a prerequisite for productive membrane association, (ii) the reaction of 11R-LOX with arachidonic acid coincided with and was driven by its Ca(2+)-mediated membrane association, and (iii) phosphatidylethanolamine and anionic phospholipids had a synergistic effect on the Ca(2+) affinity, in line with a target-activated messenger affinity mechanism [Corbin, J. A., et al. (2007) Biochemistry 46, 4322-4336]. According to the mechanism proposed in this report, 11R-LOX can bind to the membranes in two different modes and the efficiency of productive membrane binding is determined by a concerted association of Ca(2+) and lipid headgroups.     

Structural Implications of Hydrogen-Bond Energetics in Membrane Proteins Revealed by High-Pressure Spectroscopy

The light-harvesting 1 (LH1) integral membrane complex of Rhodobacter sphaeroides provides a convenient model system in which to examine the poorly understood role of hydrogen bonds (H-bonds) as stabilizing factors in membrane protein complexes. We used noncovalently bound arrays of bacteriochlorophyll chromophores within native and genetically modified variants of LH1 complexes to monitor local changes in the chromophore binding sites induced by externally applied hydrostatic pressure. Whereas membrane-bound complexes demonstrated very high resilience to pressures reaching 2.1 GPa, characteristic discontinuous shifts and broadenings of the absorption spectra were observed around 1 GPa for detergent-solubilized proteins, in similarity to those observed when specific (α or β) H-bonds between the chromophores and the surrounding protein were selectively removed by mutagenesis. These pressure effects, which were reversible upon decompression, allowed us to estimate the rupture energies of H-bonds to the chromophores in LH1 complexes. A quasi-independent, additive role of H-bonds in the α- and β-sublattices in reinforcing the wild-type LH1 complex was established. A comparison of a reaction-center-deficient LH1 complex with complexes containing reaction centers also demonstrated a stabilizing effect of the reaction center. This study thus provides important insights into the design principles of natural photosynthetic complexes.     

Global phylogeography and genetic diversity of the zoonotic tapeworm Echinococcus granulosus sensu stricto genotype G1

Echinococcus granulosus sensu stricto (s.s.) is the major cause of human cystic echinococcosis worldwide and is listed among the most severe parasitic diseases of humans. To date, numerous studies have investigated the genetic diversity and population structure of E. granulosus s.s. in various geographic regions. However, there has been no global study. Recently, using mitochondrial DNA, it was shown that E. granulosus s.s. G1 and G3 are distinct genotypes, but a larger dataset is required to confirm the distinction of these genotypes. The objectives of this study were to: (i) investigate the distinction of genotypes G1 and G3 using a large global dataset; and (ii) analyse the genetic diversity and phylogeography of genotype G1 on a global scale using near-complete mitogenome sequences. For this study, 222 globally distributed E. granulosus s.s. samples were used, of which 212 belonged to genotype G1 and 10 to G3. Using a total sequence length of 11,682?bp, we inferred phylogenetic networks for three datasets: E. granulosus s.s. (n?=?222), G1 (n?=?212) and human G1 samples (n?=?41). In addition, the Bayesian phylogenetic and phylogeographic analyses were performed. The latter yielded several strongly supported diffusion routes of genotype G1 originating from Turkey, Tunisia and Argentina. We conclude that: (i) using a considerably larger dataset than employed previously, E. granulosus s.s. G1 and G3 are indeed distinct mitochondrial genotypes; (ii) the genetic diversity of E. granulosus s.s. G1 is high globally, with lower values in South America; and (iii) the complex phylogeographic patterns emerging from the phylogenetic and geographic analyses suggest that the current distribution of genotype G1 has been shaped by intensive animal trade.     

Similarity-based large-scale distribution mapping of orchids

The expected presence/absence of a target species outside the area of actual observations is commonly estimated using statistical models or decision criteria. This investigation demonstrates a similarity-based solution for predictive mapping as an alternative to generalizing models. The maps of the expected distribution of 12 orchids were created using find sites from field observations and absence sites generated onto the observation track. The expected presence/absence of a species in a location was calculated according to the similarity between the location and selected examples of presence and absence sites. A machine learning system selected the best predictive sets for each species out of 161 cartographic and remote sensing features. The usefulness of the predictive distribution maps was expressed as the ratio of the density of find sites per track in the predicted presence area relative to the density per track in the predicted absence area. The predictive mapping was more efficient for Dactylorhiza incarnata, D. russowii, Gymnadenia conopsea, and Goodyera repens. Soil properties and the proportion of find sites for the other species in the vicinity were the most indicative site characteristics. The rarer species were found to be better indicators of the occurrence of the other species than were the more common orchids. The proposed approach—to direct subsequent field observations to sites where the occurrence of the target species was predicted but has not yet been recorded—helped discover new populations of orchids and enhance the representativeness of absence sites.     

Role Preferences of People with Multiple Sclerosis: Image-Revised,Computerized Self-Administered Version of the Control Preference Scale

Background

The Control Preference Scale (CPS) is the most frequently used measure of patients’ preferred roles in treatment decisions. We revised the original CPS and developed a new computerized patient self-administered version (eCPS). We used the eCPS to assess role preferences, and their determinants, in Italian and German people with multiple sclerosis (MS).

Methods

New cartoons were produced, based on MS health professional and patient input/feedback and previous findings, and pilot tested on 26 Italian and German MS patients. eCPS acceptability and reliability (weighted kappa statistic, wK) in comparison to the original tool, was determined in 92 MS patients who received both CPS versions in random order.

Results

The new cartoons were well accepted and easily interpreted by patients, who reported they based their choices mainly on the text and considered the images of secondary importance. eCPS reliability was moderate (wK 0.53, 95% confidence interval [CI] 0.40–0.65) and similar to the test-retest reliability of face-to-face administration assessed in a previous publication (wK 0.65, 95% CI 0.45–0.81). Higher education (odds ratio [OR] 3.74, 95% CI 1.00–14.05) and German nationality (OR 10.30, 95% CI 3.10–34.15) were associated with preference for an active role in the logistic model.

Conclusions

The newly devised eCPS was well received and considered easy to use by MS patients. Reliability was in line with that of the original version. Role preference appears affected by cultural characteristics and (borderline statistical significance) education.