Structural characterization of binding of Cu(II) to tau protein

Transition metals have been frequently recognized as risk factors in neurodegenerative disorders, and brain lesions associated with Alzheimer's disease are rich in Fe(III), Zn(II), and Cu(II). By using different biophysical techniques (nuclear magnetic resonance, circular dichroism, light scattering, and microcalorimetry), we have structurally characterized the binding of Cu(II) to a 198 amino acid fragment of the protein Tau that can mimic both the aggregation behavior and microtubule binding properties of the full-length protein. We demonstrate that Tau can specifically bind one Cu(II) ion per monomer with a dissociation constant in the micromolar range, an affinity comparable to the binding of Cu(II) to other proteins involved in neurodegenerative diseases. NMR spectroscopy showed that two short stretches of residues, (287)VQSKCGS (293) and (310)YKPVDLSKVTSKCGS (324), are primarily involved in copper binding, in agreement with mutational analysis. According to circular dichroism and NMR spectroscopy, Tau remains largely disordered upon binding to Cu(II), although a limited amount of aggregation is induced.     

Effects of Passage Through Tamarin Guts on the Germination Potential of Dispersed Seeds

Passage through tamarin guts may have an effect on seed germination potential. To examine these effects, and the variation between 2 sympatric tamarin species, we studied Saguinus mystax and S. fuscicollis in northeastern Peruvian Amazonia. For most of 39 plant species, neither germination success nor latency was modified by gut passage. Neutral effects on seed germination potential suggest that tamarins may fulfill criteria for effective seed dispersal.     

Conversion of xylose to ethanol by a novel phenol-tolerant strain of Enterobacteriaceae isolated from olive mill wastewater

A xylose-fermenting bacterium of the family Enterobacteriaceae was isolated from olive mill wastewater. It converted xylose to ethanol with a yield of 0.19 g ethanol g^–1 xylose. Although phenolic compounds normally inhibit pentose-utilizing microorganisms, this isolate was tolerant to phenol. Both the yield and the productivity of xylose fermentation decreased by 30% when phenol was added at a final concentration of 0.8 g phenol l^–1. Xylose (23 g l^–1) was totally fermented to ethanol (4.3 g l^–1) within 48 h in the absence of phenol; however, in the presence of 0.8 g phenol l^–1, only 3.3 g ethanol l^–1 was obtained from the same starting concentration of xylose after 70 h.     

Structural comparisons of the aggregates of tobacco mosaic virus protein

The coat protein of tobacco mosaic virus forms numerous aggregates, including the small A-protein, the disk, and two helical forms. The structures of the disk, the helical protein forms, and the virus are compared. Most of the differences are in the conformation of the chain between residues 89 and 113, which lies in the region of protein at the center of the virus, inside the RNA. It is disordered in the disk, but has a fixed conformation in the virus and the protein helices. The differences between the virus and the two helical protein forms are largely in the conformations of arginines and carboxylic acids in this region.     

Seasonal variation and an “outbreak” of frog predation by tamarins

We report temporal variation and an “outbreak” of frog predation by moustached tamarins, Saguinus mystax, in north-eastern Peruvian Amazonia. Frog predation rates were generally very low, but strongly increased in October 2015. Other high rates, identified by outlier analyses, were also observed in September–November of other years. Over all study years, predation rates in this 3-month period were significantly higher than those in the remainder of the year, suggesting a seasonal pattern of frog predation by tamarins. Reduced fruit availability or increased frog abundance or a combination of both may be responsible for both the seasonal pattern and the specific “outbreak” of frog predation.     

A novel model to characterize structure and function of BRCA1

BRCA1 plays a central role in DNA repair. Although N‐terminal RING and C‐terminal BRCT domains are studied well, the functions of the central region of BRCA1 are poorly characterized. Here, we report a structural and functional analysis of BRCA1 alleles and functional human BRCA1 in chicken B‐lymphocyte cell line DT40. The combination of “homologous recombineering” and “RT‐cassette” enables modifications of chicken BRCA1 gene in Escherichia coli. Mutant BRCA1 knock‐in DT40 cell lines were generated using BRCA1 mutation constructs by homologous recombination with a targeting efficiency of up to 100%. Our study demonstrated that deletion of motifs 2–9 BRCA1^{Δ/Δ181‐1415} (Caenorhabditis elegans BRCA1 mimic) or deletion of motif 1 BRCA1^{Δ/Δ126‐136} decreased cell viability following cisplatin treatment. Furthermore, deletion of motifs 5 and 6 BRCA1^{Δ/Δ525‐881} within DNA‐binding region, even the conserved 7‐amino acid deletion BRCA1^{Δ/Δ872‐878} within motif 6, caused a decreased cell viability upon cisplatin treatment. Surprisingly, human BRCA1 is functional in DT40 cells as indicated by DNA damage‐induced Rad 51 foci formation in human BRCA1 knock‐in DT40 cells. These results demonstrate that those conserved motifs within the central region are essential for DNA repair functions of BRCA1. These findings provide a valuable tool for the development of new therapeutic modalities of breast cancer linked to BRCA1.     

On the occurrence of acylated flavonoid aglycones

The known acylated flavonoid aglycones are reviewed. Their substitution patterns and their distribution in plants are discussed briefly. A new pair of flavonol esters is reported in Notholaena candida var. candida, the acetate and butyrate of isognaphalin.