Azo reductase activity of intact saccharomyces cerevisiae cells is dependent on the Fre1p component of plasma membrane ferric reductase

Unspecific bacterial reduction of azo dyes is a process widely studied in correlation with the biological treatment of colored wastewaters, but the enzyme system associated with this bacterial capability has never been positively identified. Several ascomycete yeast strains display similar decolorizing behaviors. The yeast-mediated process requires an alternative carbon and energy source and is independent of previous exposure to the dyes. When substrate dyes are polar, their reduction is extracellular, strongly suggesting the involvement of an externally directed plasma membrane redox system. The present work demonstrates that, in Saccharomyces cerevisiae, the ferric reductase system participates in the extracellular reduction of azo dyes. The S. cerevisiae Deltafre1 and Deltafre1 Deltafre2 mutant strains, but not the Deltafre2 strain, showed much-reduced decolorizing capabilities. The FRE1 gene complemented the phenotype of S. cerevisiae Deltafre1 cells, restoring the ability to grow in medium without externally added iron and to decolorize the dye, following a pattern similar to the one observed in the wild-type strain. These results suggest that under the conditions tested, Fre1p is a major component of the azo reductase activity.     

BBLN-1 is essential for intermediate filament organization and apical membrane morphology

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Imaging Sites of Inhibition of Proteolysis in Pathomimetic Human Breast Cancer Cultures by Light-Activated Ruthenium Compound

The cysteine protease cathepsin B has been causally linked to progression and metastasis of breast cancers. We demonstrate inhibition by a dipeptidyl nitrile inhibitor (compound 1) of cathepsin B activity and also of pericellular degradation of dye-quenched collagen IV by living breast cancer cells. To image, localize and quantify collagen IV degradation in real-time we used 3D pathomimetic breast cancer models designed to mimic the in vivo microenvironment of breast cancers. We further report the synthesis and characterization of a caged version of compound 1, [Ru(bpy)₂(1)₂](BF₄)₂ (compound 2), which can be photoactivated with visible light. Upon light activation, compound 2, like compound 1, inhibited cathepsin B activity and pericellular collagen IV degradation by the 3D pathomimetic models of living breast cancer cells, without causing toxicity. We suggest that caged inhibitor 2 is a prototype for cathepsin B inhibitors that can control both the site and timing of inhibition in cancer.     

Suppression of ethylene levels promotes morphogenesis in pepper (Capsicum annuum L.)

Ethylene and polyamines (PAs) are two phytohormones that play important roles during in vitro morphogenesis of several plant species. The interaction between ethylene and PAs has been of interest because both have S-adenosylmethionine as a precursor. To study the influence of ethylene and PAs on in vitro morphogenesis of an ornamental pepper, we added an ethylene scavenger, PAs, a PA inhibitor, and compounds that affect ethylene biosynthesis and activity to the regeneration medium. Regeneration frequencies increased in response to treatment with ethylene inhibitors (aminoethoxyvinylglycine and silver thiosulfate) and an ethylene scavenger (mercury perchlorate). Treatment with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid reduced the regeneration frequency, increased callus formation, and increased ethylene levels; similar results were obtained in response to treatment with the PA inhibitor methylglyoxal-bis(guanylhydrazone). By contrast, treatment with PAs (particularly spermidine and spermine) decreased ethylene levels, increased the regeneration frequency, and increased shoot bud formation. These results suggest a coordinated regulation of ethylene and polyamines because the suppression of ethylene levels using ethylene inhibitors, polyamines, or mercury perchlorate increased the in vitro regeneration frequency and morphogenic responses of Capsicum annuum L.     

Prevalence and incidence of Helicobacter pylori Infection in a healthy pediatric population in the Lisbon area

Background: Helicobacter pylori is mainly acquired in childhood. Although adult studies reported a high prevalence of H. pylori infection in Portugal, the actual rate in children remains unknown. This study aimed to determine the prevalence and the incidence of H. pylori infection in an asymptomatic pediatric population of the Lisbon area and to correlate prevalence with sociodemographic determinants. Materials and Methods: Helicobacter pylori infection was determined by stool antigen test in 844 asymptomatic children (age 0–15 years; 49.4% boys). For the incidence study, H. pylori‐negative children in the prevalence study were followed‐up every 6 months over a 3‐year period. Results: The global prevalence of H. pylori infection was 31.6%, increasing with age (19.9, 37.0 and 51.5%, in age groups 0–5, 6–10, and 11–15, respectively), but was similar among genders (34.5% in boys and 28.4% in girls). Older age and attendance of nursery/kindergarten during preschool constituted independent risk factors. The overall estimated incidence was 11.6 per 100 child‐years (CY). Although 47.5% of children acquired H. pylori infection before 5 years of age, the mean age of acquisition was 6.3. The incidence of infection was similar among the three age groups (11.5, 13.0, and 10.5 per 100 CY, in age groups 0–5, 6–10, and 11–15, respectively). Conclusions: The prevalence of H. pylori infection in the Portuguese pediatric population is still high. Although this study confirmed that the highest acquisition rate occurs at young age, it showed that in high‐prevalence populations, older children can also acquire H. pylori infection at a rate similar to that of young children.     

Thermodynamic Framework of the Interaction between Protein and Solvent Drives Protein Folding

Abstract

We use internal coordinate molecular mechanics calculations to study the impact of abasic sites on the conformation and the mechanics of the DNA double helix. Abasic sites, which are common mutagenic lesions, are shown to locally modify both the groove geometry and the curvature of DNA in a sequence dependent manner. By controlled twisting and bending, it is also shown that these lesions modify the deformability of the duplex, generally increasing its flexibility, but again to an extent which depends on the nature of the abasic site and on the surrounding base sequence. Both the conformational and mechanical influence of this type of DNA damage may be significant for recognition and repair mechanisms.     

Understanding the substituent effect on the acidity of alcohols and para-substituted phenols

We carried out Hartree–Fock (HF) and density functional theory calculations on the conjugated bases of phenols and alcohols for 23 compounds and analysed their acid–base behaviour using molecular orbital (MO) energies and their dependence on solvent effects. Despite the well-known correlation between highest-occupied MO (HOMO) energies and proton affinity (PA), we observed that HOMO energies are inadequate to describe the acid–base behaviour of these compounds. Therefore, we established a criterion to identify the best frontier MO for describing PA values and also to understand why the HOMO approach fails. The MO that fits our criterion provided very good correlations with PA values, much better than those obtained by the HOMO energies. Since the frontier MOs are those which drive the acid–base reactions in each compound, they were called frontier effective-for-reaction MOs, or FERMOs. By using the FERMO concept, the reactions that are HOMO driven, and those that are not, can be better explained, independent of the calculation method used, since both HF and Kohn–Sham methodologies lead to the same FERMO.     

Molecular modeling studies of Yersinia pestis dihydrofolate reductase

Considering the risk represented by plague today as a potential biological warfare agent, we propose cytosolic Yersinia pestis dihydrofolate reductase (YpDHFR) as a new target to the design of selective plague chemotherapy. This enzyme has a low homology with the human enzyme and its crystallographic structure has been recently deposited in the Protein Data Bank (PDB). Comparisons of the docking energies and molecular dynamic behaviors of five known DHFR inhibitors inside a 3D model of YpDHFR (adapted from the crystallographic structure) and human DHFR (HssDHFR), revealed new potential interactions and suggested insights into the design of more potent HssDHFR inhibitors as well as selective inhibitors for YpDHFR.     

Impact of native vegetation cover near crops on the occurrence and molecular diversity of fire ants

Solenopsis invicta and Solenopsis saevissima are the most common fire ants in Brazil. Environmental disturbances favour the colony dispersal of both species, particularly those with an anthropogenic origin. However, the frequencies of the species can vary according to the amount of anthropogenic disturbances. Crops near native vegetation fragments is a common landscape in the Brazilian Atlantic Forest. Here, we analyse if there is influence of native vegetation cover on the occurrence of these fire ants and their molecular diversity in crops. Our hypothesis is that these species are antagonistic in terms of occurrence and molecular diversity when compared in the same habitat. We selected crops near fragments with around 50% of native vegetation cover, a percentage informative enough to detect biological responses from insects belonging to a same order. Nests were collected and the species were identified using external morphology, and mtDNA COI sequences. We reject our hypothesis, which suggest that the species colonize the vegetation patches around crops in a similar way. Solenopsis invicta is not limited by vegetation cover, and has a high haplotype diversity when compared to S. saevissima, particularly when the vegetation cover is greater than 50%. Additionally, the vegetation cover seems to not have influence in the total number of haplotypes, but the species have haplotypes that are exclusive to each landscape. Our findings suggest that S. invicta is expanding to native vegetation areas that it has not occupied before, as S. saevissima was dominant there.     

Apoptosis in transgenic mice expressing the P301L mutated form of human tau

The rTg4510 mouse is a tauopathy model, characterized by massive neurodegeneration in Alzheimer's disease (AD)-relevant cortical and limbic structures, deficits in spatial reference memory, and progression of neurofibrillary tangles (NFT). In this study, we examined the role of apoptosis in neuronal loss and associated tau pathology. The results showed that DNA fragmentation and caspase-3 activation are common in the hippocampus and frontal cortex of young rTg4510 mice. These changes were associated with cleavage of tau into smaller intermediate fragments, which persist with age. Interestingly, active caspase-3 was often co-localized with cleaved tau. In vitro, fibrillar Abeta(1-42) resulted in nuclear fragmentation, caspase activation, and caspase-3-induced cleavage of tau. Notably, incubation with the antiapoptotic molecule tauroursodeoxycholic acid abrogated apoptosis-mediated cleavage of tau in rat cortical neurons. In conclusion, caspase-3-cleaved intermediate tau species occurred early in rTg54510 brains and preceded cell loss in Abeta-exposed cultured neurons. These results suggest a potential role of apoptosis in neurodegeneration.