Effect of alkyl side chain variation on the electron-transfer activity of ubiquinone derivatives

The effect of the alkyl side chain of the ubiquinone molecule on the electron-transfer activity of ubiquinone in mitochondrial succinate-cytochrome c reductase is studied by using synthetic ubiquinone derivatives that possess the basic ubiquinone structure of 2,3-dimethoxy-5-methyl-1,4-benzoquinone with different alkyl side chains at the 6-position. The alkyl side chains vary in chain length, degree of saturation, and location of double bonds. When a ubiquinone derivative is used as an electron acceptor for succinate-ubiquinone reductase, an alkyl side chain of six carbons is needed to obtain the maximum activity. However, when it serves as an electron donor for ubiquinol-cytochrome c reductase or as a mediator in succinate-cytochrome c reductase, an alkyl side chain of 10 carbons gives maximal efficiency. Introduction of one or two isolated double bonds into the alkyl side chain of the ubiquinone molecule has little effect on electron-transfer activity. However, a conjugated double bond system in the alkyl side chain drastically reduces electron-transfer efficiency. The effect of the conjugated double bond system on the electron-transferring efficiency of ubiquinone depends on its location in the alkyl side chain. When location is far from the benzoquinone ring, the effect is minimal. These observations together with the results obtained from photoaffinity-labeling studies lead us to conclude that flexibility in the portion of the alkyl side chain immediately adjacent to the benzoquinone ring is required for the electron-transfer activity of ubiquinone.     

Polyphyly of Asian Tree Toads,Genus Pedostibes Günther, 1876 (Anura: Bufonidae), and the Description of a New Genus from Southeast Asia

The Asian Tree Toad genus Pedostibes, as currently understood, exhibits a conspicuously disjunct distribution, posing several immediate questions relating to the biogeography and taxonomy of this poorly known group. The type species, P. tuberculosus and P. kempi, are known only from India, whereas P. hosii, P. rugosus, and P. everetti are restricted to Southeast Asia. Several studies have shown that these allopatric groups are polyphyletic, with the Indian Pedostibes embedded within a primarily South Asian clade of toads, containing the genera Adenomus, Xanthophryne, and Duttaphrynus. Southeast Asian Pedostibes on the other hand, are nested within a Southeast Asian clade, which is the sister lineage to the Southeast Asian river toad genus Phrynoidis. We demonstrate that Indian and Southeast Asian Pedostibes are not only allopatric and polyphyletic, but also exhibit significant differences in morphology and reproductive mode, indicating that the Southeast Asian species’ are not congeneric with the true Pedostibes of India. As a taxonomic solution, we describe a new genus, Rentapia gen. nov. to accommodate the Southeast Asian species.     

Intra- and inter-specific effects of mast seeding on seed fates of two sympatric <Emphasis Type="Italic">Corylus</Emphasis> species

We released seeds of two sympatric tree species, Corylus mandshurica (seed with thinner seed hull, higher nutrition) and C. heterophylla (seeds with thicker seed hull, lower nutrition) in the masting year of C. mandshurica in 2008, and C. heterophylla in 2009, respectively, to investigate how seed masting of the two sympatric Corylus species affects seed removal and dispersal fitness of the two species differently at both intra- and inter-specific levels. At intra-specific level, the authors found mast seeding of both C. mandshurica and C. heterophylla significantly reduced seed removal, seed consumption, but increased seed dispersal distance and seed dispersal fitness of the released seeds. Mast seeding of C. mandshurica increased seed caching of C. mandshurica. At inter-specific level, the authors found mast seeding of C. mandshurica reduced seed removal of C. heterophylla, but mast seeding of C. heterophylla did not significantly reduce seed removal of C. mandshurica. Mast seeding of C. mandshurica reduced seed consumption of C. heterophylla, while mast seeding of C. heterophylla reduced seed consumption of C. mandshurica. We found mast seeding of C. mandshurica significantly reduced seed dispersal distance of C. heterophylla, while mast seeding of C. heterophylla significantly increased seed dispersal distance of C. mandshurica. We found that mast seeding of C. mandshurica significantly increased seed dispersal fitness of C. heterophylla, while mast seeding of C. heterophylla did not significantly increase seed dispersal fitness of C. mandshurica. More studies are needed to reveal the ecological consequences of mast seeding at inter-specific or community-level. Seed traits may attribute the differences of mast seeding at inter-specific level. Because seeds with thinner seed hull and higher nutrition were more harvested and eaten by rodents, mast seeding of C. mandshurica might have reduced seed removal and seed consumption, but increased dispersal fitness of C. heterophylla (seeds with thicker seed hull, lower nutrition). Therefore, synchrony among species is, or is not, selectively beneficial to the focus species depends on seed traits which determine gains from mast seeding at inter-specific level.     

Calcium binding mode of gamma-carboxyglutamic acids in conantokins.

Conantokin-T (con-T) and conantokin-G (con-G) are two highly homologous peptide toxins found in Conus venom. The former is a 21-residue peptide with four gamma-carboxyglutamic acid (Gla) residues (at positions 3, 4, 10 and 14), while the latter is a 17-residue peptide with five gamma-carboxyglutamic acid residues (at positions 3, 4, 7, 10 and 14). Despite the apparent similarity in number and relative positions of the gamma-carboxyglutamic acid residues, (113)Cd-NMR studies indicated a distinct metal binding behavior for con-G and con-T. There appears to be four binding sites in con-G in contrast to one metal binding site in con-T. To elucidate the mode of calcium binding by the gamma-carboxyglutamic acid residues in these conantokins, we designed various analogous peptides with their gamma-carboxyglutamic acid replaced by other amino acid residues. (113)Cd-NMR experiments on conantokin analogues reveal that the major difference in the number of metal binding sites between con-G and con-T is due to the residue at position 7. We also performed molecular simulations to calculate the relative binding free energies of several potential binding sites. Based on our theoretical and experimental results, we propose a 'four-site' binding model for conantokin-G and a 'single-site' binding model for conantokin-T.     

Human endothelin converting enzyme-2 (ECE2): characterization of mRNA species and chromosomal localization.

Generation of the functionally pleiotropic members of the endothelin vasoactive peptide family is critically catalyzed by unique type II metalloproteases, termed endothelin converting enzymes (ECE). Isolation of human ECE-2 (EC 3.4.24.71) cDNAs revealed deduced open reading frames of 787 and 765 amino acids with approximately 60% identity with human ECE-1. Characterization of mRNA variants revealed mRNA structural diversity at the 5'-terminus. Two mRNA species exist containing distinct first and second exons. Furthermore, in one of these species, an in-frame deletion of the intracytoplasmic domain removed 29 amino acids. Because of the previously reported human genetic diseases ascribed to germline mutations of member genes of the endothelin family, ECE2 was localized in human chromosomes with fluorescence in situ hybridization and radiation hybrid mapping to 3q28-q29 and SHGC-20171/D3S1571, respectively.     

Chewing lice from high‐altitude and migrating birds in Yunnan,China, with descriptions of two new species of Guimaraesiella

In total, 366 birds representing 55 species in 24 families and eight orders, were examined for chewing lice (Phthiraptera: Amblycera, Ischnocera) in two high‐altitude localities in Yunnan Province, China. In Ailaoshan, almost all of the birds examined were resident passeriforms, of which 36% were parasitized by chewing lice. In Jinshanyakou, most birds were on migration, and included both passerine and non‐passerine birds. Of the passerine birds caught in Jinshanyakou, only one bird (0.7%) was parasitized by chewing lice. The prevalence of Myrsidea and Brueelia‐complex lice on birds caught in Ailaoshan was higher than in previous reports. Of the chewing lice identifiable to species level, three represent new records for China: Actornithophilus hoplopteri (Mjöberg, 1910), Maculinirmus ljosalfar Gustafsson & Bush, 2017 and Quadraceps sinensis Timmermann, 1954. In total, 17 new host records are included, of which we describe two as new species in the Brueelia‐complex: Guimaraesiella (Cicchinella) ailaoshanensis sp. nov. ex Schoeniparus dubius dubius (Hume, 1874) and G. (C.) montisodalis sp. nov. ex Fulvetta manipurensis tonkinensis Delacour & Jabouille, 1930. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:9FC3D8EE‐2CED‐4DBE‐A1DB‐471B71260D27 .     

The alkene monooxygenase from Xanthobacter Py2 is a binuclear non-haem iron protein closely related to toluene 4-monooxygenase

The genes encoding the six polypeptide components of the alkene monooxygenase from Xanthobacter Py2 have been sequenced. The predicted amino acid sequence of the first ORF shows homology with the iron binding subunits of binuclear non-haem iron containing monooxygenases including benzene monooxygenase, toluene 4-monooxygenase (>60% sequence similarity) and methane monooxygenase (>40% sequence similarity) and that the necessary sequence motifs associated with iron co-ordination are also present. Secondary structure prediction based on the amino acid sequence showed that the predominantly α-helical structure that surrounds the binuclear iron binding site was conserved allowing the sequence to be modelled on the co-ordinates of the methane monooxygenase α-subunit. Significant differences in the residues forming the hydrophobic cavity which forms the substrate binding site are discussed with reference to the differences in reaction specificity and stereospecificity of binuclear non-haem iron monooxygenases.