Depletion of Cognate Charged Transfer RNA Causes Translational Frameshifting within the Expanded CAG Stretch in Huntingtin

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Highlights? Expanded CAG stretches are prone to translational frameshifting ? Depletion of the charged, cognate tRNA causes translational frameshifting ? Frequency of translational frameshifting correlates with the CAG repeat length ? Frameshifted species modulate the aggregation course of the parental protein     

Fluorescence spectroscopic studies of pressure effects on Na+,K(+)-ATPase reconstituted into phospholipid bilayers and model raft mixtures

To contribute to the understanding of membrane protein function upon application of pressure as relevant for understanding, for example, the physiology of deep sea organisms or for baroenzymological biotechnical processes, we investigated the influence of hydrostatic pressure on the activity of Na+,K+-ATPase enriched in the plasma membrane from rabbit kidney outer medulla using a kinetic assay that couples ATP hydrolysis to NADH oxidation. The data show that the activity of Na+,K+-ATPase is reversibly inhibited by pressures below 2 kbar. At higher pressures, the enzyme is irreversibly inactivated. To be able to explore the effect of the lipid matrix on enzyme activity, the enzyme was also reconstituted into various lipid bilayer systems of different chain length, conformation, phase state, and heterogeneity including model raft mixtures. To yield additional information on the conformation and phase state of the lipid bilayer systems, generalized polarization values by the Laurdan fluorescence technique were determined as well. Incorporation of the enzyme leads to a significant increase of the lipid chain order. Generally, similar to the enzyme activity in the natural plasma membrane, high hydrostatic pressures lead to a decline of the activity of the enzyme reconstituted into the various lipid bilayer systems, and in most cases, a multi-phasic behavior is observed. Interestingly, in the low-pressure region, around 100 bar, a significant increase of activity is observed for the enzyme reconstituted into DMPC and DOPC bilayers. Above 100-200 bar, this activity enhancement is followed by a steep decrease of activity up to about 800 bar, where a more or less broad plateau value is reached. The enzyme activity decreases to zero around 2 kbar for all reconstituted systems measured. A different scenario is observed for the effect of pressure on the enzyme activity in the model raft mixture. The coexistence of liquid-ordered and liquid-disordered domains with the possibility of lipid sorting in this lipid mixture leads to a reduced pressure sensitivity in the medium-pressure range. The decrease of ATPase activity may be induced by an increasing hydrophobic mismatch, leading to a decrease of the conformational dynamics of the protein and eventually subunit rearrangement. High pressures, above about 2.2 kbar, irreversibly change protein conformation, probably because of the dissociation and partial unfolding of the subunits.     

Differential effects of abandonment on the demography of the grassland perennial Succisa pratensis

Abandonment of traditional land-use practices can have strong effects on the abundance of species occurring in agricultural landscapes. However, the precise mechanisms by which individual performance and population dynamics are affected are still poorly understood. To assess how abandonment affects population dynamics of Succisa pratensis we used data from a 4-year field study in both abandoned and traditionally grazed areas in moist and mesic habitats to parameterize integral projection models. Abandoned populations had a lower long-term stochastic population growth rate (λ _S = 0.90) than traditionally managed populations (λ _S = 1.08), while λ _S did not differ between habitat types. The effect of abandonment differed significantly between years and had opposed effects on different vital rates. Individuals in abandoned populations experienced higher mortality rates and lower seedling establishment, but had higher growth rates and produced more flower heads per plant. Population viability analyses, based on a population survey of the whole study area in combination with our demographic models, showed that 32 % of the populations face a high risk of extinction (>80 %) within 20 years. These results suggest that immediate changes in management are needed to avoid extinctions and further declines in population sizes. Stochastic elasticity analyses and stochastic life table response experiments indicated that management strategies would be most effective if they increase survival of small plants as well as seedling establishment, while maintaining a high seed production. This may be achieved by varying the grazing intensity between years or excluding grazers when plants are flowering.     

Rapid microarray‐based DNA genoserotyping of Escherichia coli

In this study, an improvement in the oligonucleotide‐based DNA microarray for the genoserotyping of Escherichia coli is presented. Primer and probes for additional 70 O antigen groups were developed. The microarray was transferred to a new platform, the ArrayStrip format, which allows high through‐put tests in 96‐well formats and fully automated microarray analysis. Thus, starting from a single colony, it is possible to determine within a few hours and a single experiment, 94 of the over 180 known O antigen groups as well as 47 of the 53 different H antigens. The microarray was initially validated with a set of defined reference strains that had previously been serotyped by conventional agglutination in various reference centers. For further validation of the microarray, 180 clinical E. coli isolates of human origin (from urine samples, blood cultures, bronchial secretions, and wound swabs) and 53 E. coli isolates from cattle, pigs, and poultry were used. A high degree of concordance between the results of classical antibody‐based serotyping and DNA‐based genoserotyping was demonstrated during validation of the new 70 O antigen groups as well as for the field strains of human and animal origin. Therefore, this oligonucleotide array is a diagnostic tool that is user‐friendly and more efficient than classical serotyping by agglutination. Furthermore, the tests can be performed in almost every routine lab and are easily expanded and standardized.