Presence of xyloglucan-like polysaccharide in Spirogyra and possible involvement in cell–cell attachment

By methylation analysis, it was found that the cell walls of Spirogyra contained 4,6-linked glucose, 4-linked glucose and terminal xylose, which could be components of xyloglucan. Immunocytochemical analysis was carried out using an anti-serum against xyloglucan. After removal of pectic substances, the cell walls of both rhizoid cells and inner cells were stained. Crude protein extract from Spirogyra had a hydrolase activity for xyloglucans. In addition, the exogenously applied xyloglucan prevented the detachment of the cell wall of the severed cell. Involvement of xyloglucan-like polysaccharide in cell–cell attachment was discussed.     

Asian promise: the state and future of collaborations in neuroscience

As investment in science and technology continues to grow in Asia, countries such as China, Japan and Singapore are witnessing great improvements in their neuroscience research environments; this is reflected in the opening of new research institutions and in the influx of neuroscientists trained abroad. Collaborative projects between researchers in these countries and laboratories in the United States and Europe are not only helping to shape these institutions, they are also leading to a surge in high-quality publications in both basic and translational neuroscience, resulting in increasing international recognition. Nature Reviews Neuroscience asks four neuroscientists about their collaborative experiences and the impact that such collaborations are having on neuroscience research.     

A new family of H3 receptor antagonists based on the natural product Conessine

A new family of Histamine H(3) receptor antagonists (5a-t) has been prepared based on the structure of the natural product Conessine, a known H(3) antagonist. Several members of the new series are highly potent and selective binders of rat and human H(3) receptors and display inverse agonism at the human H(3) receptor. Compound 5n exhibited promising rat pharmacokinetic properties and demonstrated functional antagonism of the H(3) receptor in an in-vivo pharmacological model.     

Antimalarial activity enhancement in hydroxymethylcarbonyl (HMC) isostere-based dipeptidomimetics targeting malarial aspartic protease plasmepsin

Plasmepsin (Plm) is a potential target for new antimalarial drugs, but most reported Plm inhibitors have relatively low antimalarial activities. We synthesized a series of dipeptide-type HIV protease inhibitors, which contain an allophenylnorstatine-dimethylthioproline scaffold to exhibit potent inhibitory activities against Plm II. Their activities against Plasmodium falciparum in the infected erythrocyte assay were largely different from those against the target enzyme. To improve the antimalarial activity of peptidomimetic Plm inhibitors, we attached substituents on a structure of the highly potent Plm inhibitor KNI-10006. Among the derivatives, we identified alkylamino compounds such as 44 (KNI-10283) and 47 (KNI-10538) with more than 15-fold enhanced antimalarial activity, to the sub-micromolar level, maintaining their potent Plm II inhibitory activity and low cytotoxicity. These results suggest that auxiliary substituents on a specific basic group contribute to deliver the inhibitors to the target Plm.     

Unfolding and aggregation of transthyretin by the truncation of 50 N-terminal amino acids

Senile systemic amyloidosis (SSA) is caused by amyloid deposits of wild-type transthyretin in various organs. Amyloid deposits from SSA contain large amounts of the C-terminal fragments starting near amino acid residue 50 as well as full-length transthyretin. Although a number of previous studies suggest the importance of the C-terminal fragments in the pathogenesis of SSA, little is known about the structure and aggregation properties of the C-terminal fragments of transthyretin. To understand the role of C-terminal fragments in SSA, we examined the effects of the truncation of the N-terminal portions on the structure and aggregation properties of wild-type transthyretin. The deletion mutant lacking 50 N-terminal residues was largely unfolded in terms of secondary and tertiary structure, leading to self-assembly into spherical aggregations under nearly physiological conditions. By contrast, the deletion mutant lacking 37 N-terminal residues did not have a strong tendency to aggregate, although it also adopted a largely unfolded conformation. These results suggest that global unfolding of transthyretin by proteolysis near amino acid residue 50 is an important step of self-assembly into aggregations in SSA.     

Construction of a binary vector for knockout and expression analysis of rice blast fungus genes

We developed an efficient method to analyze gene function and expression of the rice blast fungus. We constructed a GATEWAY binary vector, which generates a gene-targeted disruptant carrying a green fluorescent protein gene under the native promoter of the target gene. Using this method, the knockout efficiency and expression patterns of two hypothetical genes were determined.     

Purple acid phosphatase in the walls of tobacco cells

Purple acid phosphatase isolated from the walls of tobacco cells appears to be a 220 kDa homotetramer composed of 60 kDa subunits, which is purple in color and which contains iron as its only metal ion. Although the phosphatase did not require dithiothreitol for activity and was not inhibited by phenylarsine oxide, the enzyme showed a higher catalytic efficiency (k_cat/K_m) for phosphotyrosine-containing peptides than for other substrates including p-nitrophenyl-phosphate and ATP. The phosphatase formed as a 120 kDa dimer in the cytoplasm and as a 220 kDa tetramer in the walls, where Brefeldin A blocked its secretion during wall regeneration. According to our double-immunofluorescence labeling results, the enzyme might be translocated through the Golgi apparatus to the walls at the interphase and to the cell plate during cytokinesis.     

Proteomic analysis of highly purified peroxisomes from etiolated soybean cotyledons

To identify previously unknown peroxisomal proteins, we establishedan optimized method for isolating highly purified peroxisomesfrom etiolated soybean cotyledons using Percoll density gradientcentrifugation followed by iodixanol density gradient centrifugation.Proteins in highly purified peroxisomes were separated by two-dimensionalPAGE. We performed peptide mass fingerprinting of proteins separatedin the gel with matrix-assisted laser desorption ionizationtime-of-flight mass spectrometry and used the peptide mass fingerprintsto search a non-redundant soybean expressed sequence tag database.We succeeded in assigning 92 proteins to 70 sequences in thedatabase. Among them, proteins encoded by 30 sequences werejudged to be located in peroxisomes. These included enzymesfor fatty acid β-oxidation, the glyoxylate cycle, photorespiratoryglycolate metabolism, stress response and metabolite transport.We also show experimental evidence that plant peroxisomes containa short-chain dehydrogenase/reductase family protein, enoyl-CoAhydratase/isomerase family protein, 3-hydroxyacyl-CoA dehydrogenase-likeprotein and a voltage-dependent anion-selective channel protein.