Structure of the N-terminal domain of PEX1 AAA-ATPase. Characterization of a putative adaptor-binding domain

Peroxisomes are responsible for several pathways in primary metabolism, including beta-oxidation and lipid biosynthesis. PEX1 and PEX6 are hexameric AAA-type ATPases, both of which are indispensable in targeting over 50 peroxisomal resident proteins from the cytosol to the peroxisomes. Although the tandem AAA-ATPase domains in the central region of PEX1 and PEX6 are highly similar, the N-terminal sequences are unique. To better understand the distinct molecular function of these two proteins, we analyzed the unique N-terminal domain (NTD) of PEX1. Extensive computational analysis revealed weak similarity (<10% identity) of PEX1 NTD to the N-terminal domains of other membrane-related type II AAA-ATPases, such as VCP (p97) and NSF. We have determined the crystal structure of mouse PEX1 NTD at 2.05-A resolution, which clearly demonstrated that the domain belongs to the double-psi-barrel fold family found in the other AAA-ATPases. The N-domains of both VCP and NSF are structural neighbors of PEX1 NTD with a 2.7- and 2.1-A root mean square deviation of backbone atoms, respectively. Our findings suggest that the supradomain architecture, which is composed of a single N-terminal domain followed by tandem AAA domains, is a common feature of organellar membrane-associating AAA-ATPases. We propose that PEX1 functions as a protein unfoldase in peroxisomal biogenesis, using its N-terminal putative adaptor-binding domain.     

Species richness and species composition of fungal communities associated with cellulose decomposition at different altitudes on the Tibetan Plateau

Aims The aims of this study were to compare the fungal communities developing on cotton strips at three different altitudes on the Tibetan Plateau and to assess the environmental variables influencing them.Methods Cotton strips that had been buried in soil for a year were sampled at three sites at different altitudes (4500, 4950 and 5200 m) located on a southeast-facing slope on the Nyainqentanglha Mountains near Damxung. The fungi on the cotton strips were isolated using a modified washing method. The decomposition abilities and colony growth properties of the major species cultured in pure-culture conditions were investigated and compared. Canonical correspondence analysis (CCA) was used to evaluate the relationships between fungal community composition and environmental variables (altitude, soil depth, soil water content [SWC], plant root mass and gravel content).Important findings A total of 24 species were isolated from the cotton strips, and 12 species occurred frequently and were regarded as major species. The number of fungal species was lower at the 4950-m altitude site than at the other two sites, indicating that not only altitude but also other factors affected the number of species present. All of the major species were able to decompose the cotton strips. In the CCA ordination, automatic forward selection revealed that altitude, SWC and plant root mass significantly affected fungal species composition. Our results suggest that species number and the composition of cellulolytic fungal communities are highly correlated with environmental variables as well as altitude in the alpine meadow on the Tibetan Plateau.     

Possible Host Adaptation as an Evolution Factor of Cowpea aphid‐borne mosaic virus Deduced by Coat Protein Gene Analysis

Cowpea aphid‐borne mosaic virus (CABMV) causes major diseases in cowpea and passion flower plants in Brazil and also in other countries. CABMV has also been isolated from leguminous species including, Cassia hoffmannseggii, Canavalia rosea, Crotalaria juncea and Arachis hypogaea in Brazil. The virus seems to be adapted to two distinct families, the Passifloraceae and Fabaceae. Aiming to identify CABMV and elucidate a possible host adaptation of this virus species, isolates from cowpea, passion flower and C. hoffmannseggii collected in the states of Pernambuco and Rio Grande do Norte were analysed by sequencing the complete coat protein genes. A phylogenetic tree was constructed based on the obtained sequences and those available in public databases. Major Brazilian isolates from passion flower, independently of the geographical distances among them, were grouped in three different clusters. The possible host adaptation was also observed in fabaceous‐infecting CABMV Brazilian isolates. These host adaptations possibly occurred independently within Brazil, so all these clusters belong to a bigger Brazilian cluster. Nevertheless, African passion flower or cowpea‐infecting isolates formed totally different clusters. These results showed that host adaptation could be one factor for CABMV evolution, although geographical isolation is a stronger factor.     

Valproic Acid-Induced Anxiety and Depression Behaviors are Ameliorated in p39 Cdk5 Activator-Deficient Mice

Neurochemical Research - Valproic acid (VPA) is a drug used for the treatment of epilepsy, seizures, migraines, and bipolar disorders. Cyclin-dependent kinase 5 (Cdk5) is a Ser/Thr kinase activated...     

A Modification of Mayer's Tannic Acid-Ferric Chloride Staining Method for Demonstrating Cellular Membranous Systems for Light Microscopy

To observe cellular membranous systems under a light microscope, we modified Mayer's tannic acid-ferric chloride stain method by adding a treatment with hematoxylin after the original procedure. We used the modified tannic acid-ferric chloride (MTA-Fe) stain method to examine kidneys, liver, heart, trachea, epididymides and other organs of rats and dogs. The MTA-Fe stain clearly demonstrated the basement membrane, brush border, basolateral invaginations and cell processes in the kidneys which enabled easy differentiation of the S1 and S3 segments of proximal convoluted tubules. Our technique also demonstrated hepatic cell membranes and bile canaliculi in the liver, cross striations and longitudinal traveling of myofibrils in the heart, cilia of the epithelial cells in the trachea, and stereocilia and terminal bars in the epididymis. The MTA-Fe stain is a convenient method to visualize cellular membranous systems even for light microscopy. The stain has the advantages of using no toxic materials, simple and easy technique, little variation of staining results, and little fading for several months after staining.     

Pesticide formulations: Innovations and developments

Book Review

Pesticide formulations: Innovations and developmentsB. Cross and H.B. Scher (Eds.), ACS Symposium Series 371. Washington DC: American Chemical Society, 1988. xi + 288 pages. £54.00. ISBN 0-8412-1483-2     

Proteomic identification of protein targets for 15-deoxy-Δ(12,14)-prostaglandin J2 in neuronal plasma membrane

15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)) is one of factors contributed to the neurotoxicity of amyloid β (Aβ), a causative protein of Alzheimer's disease. Type 2 receptor for prostaglandin D(2) (DP2) and peroxysome-proliferator activated receptorγ (PPARγ) are identified as the membrane receptor and the nuclear receptor for 15d-PGJ(2), respectively. Previously, we reported that the cytotoxicity of 15d-PGJ(2) was independent of DP2 and PPARγ, and suggested that 15d-PGJ(2) induced apoptosis through the novel specific binding sites of 15d-PGJ(2) different from DP2 and PPARγ. To relate the cytotoxicity of 15d-PGJ(2) to amyloidoses, we performed binding assay [(3)H]15d-PGJ(2) and specified targets for 15d-PGJ(2) associated with cytotoxicity. In the various cell lines, there was a close correlation between the susceptibilities to 15d-PGJ(2) and fibrillar Aβ. Specific binding sites of [(3)H]15d-PGJ(2) were detected in rat cortical neurons and human bronchial smooth muscle cells. When the binding assay was performed in subcellular fractions of neurons, the specific binding sites of [(3)H]15d-PGJ(2) were detected in plasma membrane, nuclear and cytosol, but not in microsome. A proteomic approach was used to identify protein targets for 15d-PGJ(2) in the plasma membrane. By using biotinylated 15d-PGJ(2), eleven proteins were identified as biotin-positive spots and classified into three different functional proteins: glycolytic enzymes (Enolase2, pyruvate kinase M1 (PKM1) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH)), molecular chaperones (heat shock protein 8 and T-complex protein 1 subunit α), cytoskeletal proteins (Actin β, F-actin-capping protein, Tubulin β and Internexin α). GAPDH, PKM1 and Tubulin β are Aβ-interacting proteins. Thus, the present study suggested that 15d-PGJ(2) plays an important role in amyloidoses not only in the central nervous system but also in the peripheral tissues.     

Possible evidence of contamination by catechins in deconjugation enzymes from Helix pomatia and Abalone entrails

β-Glucuronidase and sulfatase are the major deconjugating enzymes used in the cleavage of the glucuronate and sulfate moieties, respectively, from certain conjugated food factors including polyphenols. In the present study, we found that compounds having the same molecular weights as catechins were present in Helix pomatia- and/or Abalone entrails-derived β-glucuronidase and sulfatase by liquid chromatography tandem mass spectrometry (LC-MS/MS) with multiple reaction monitoring methods. On the other hand, the same molecular weights as catechins were undetectable in Escherichia coli-derived β-glucuronidase and Aerobacter aerogenes-derived sulfatase. By high performance liquid chromatography, enzyme-derived catechins were not detected because of approximately 1,000-fold lower sensitivity as compared to LC-MS/MS. These results suggest that the catechins in these enzymes might be attributed to the diets of the organisms as the enzyme sources.     

External and internal flavonoids from Madagascarian Uncarina species (Pedaliaceae)

External and internal flavonoids were isolated from 12 Uncarina taxa (Pedaliaceae), endemic to Madagascar. Four flavone aglycones, tricetin 7,3′,5′-trimethyl ether, tricetin 7,4′,5′-trimethyl ether, 5,3′-dihydroxy-6,7,4′,5′-tetramethoxyflavone and eupatorin were isolated from leaf wax of seven Uncarina taxa, Uncarina grandidieri, Uncarina decaryi, Uncarina abbreviata, Uncarina turicana, Uncarina platycarpa, Uncarina leandrii var. leandrii and Uncarina peltata, but not Uncarina stellulifera, Uncarina perrieri, Uncarina sakalava, Uncarina leptocarpa and U. leandrii var. rechbergeri. Furthermore, eight flavonoid glycosides were isolated from the leaves. Major glycosides were apigenin and luteolin 7-O-glucuronides and occurred in all the Uncarina taxa examined, except the absence of the former compound in U. peltata. Other glycosides were identified as hispidulin, jaceosidin, chrysoeriol and tricin 7-O-glucuronides, and luteolin 7,4′-di-O-glucuronide and a flavonol, isorhamnetin 3-O-diglucoside. From the results described above, methylated flavone aglycones and glucuronides were chemical characters of the leaves of Uncarina species, and also may be those of the family Pedaliaceae. Besides, an anthocyanin, two flavonols and three flavones were isolated from the flowers of U. grandidieri, and identified as cyanidin 3-O-rutinoside (anthocyanin), quercetin and isorhamnetin 7-O-glucuronides (flavonols) and apigenin, luteolin and jaceosidin 7-O-glucuronides (flavones).