Involvement of Ca in globular adiponectin-induced reactive oxygen species

Globular adiponectin (gAd) induces the generation of reactive oxygen species (ROS) and nitric oxide (NO) in the murine macrophage cell line RAW 264. We investigated the role of Ca²⁺ in gAd-induced ROS and NO generation. Pretreatment with BAPTA-AM, a selective chelator of intracellular Ca²⁺ ([Ca²⁺]_i), partially reduced gAd-induced generation of ROS and NO in gAd-treated RAW 264 cells. The lowest [Ca²⁺]_i occurred 30 min after gAd treatment, after which [Ca²⁺]_i increased continually and exceeded the initial level. The mitochondrial Ca²⁺ ([Ca²⁺]_m) detected by Rhod-2 fluorescence started to increase at 6 h after gAd treatment. Pretreatment with a NAD(P)H oxidase inhibitor, diphenyleneiodonium, prevented the reduction of [Ca²⁺]_i in the early phase after gAd treatment. Calcium depletion by BAPTA-AM had no effect on the gAd-induced [Ca²⁺]_m oscillation. The administration of a specific calmodulin inhibitor, calmidazolium, significantly suppressed gAd-induced ROS and NO generation and NOS activity.     

Cloning, expression, and pore-forming properties of mature and precursor forms of pleurotolysin, a sphingomyelin-specific two-component cytolysin from the edible mushroom Pleurotus ostreatus

Pleurotolysin, a sphingomyelin-specific cytolysin consisting of A (17 kDa) and B (59 kDa) components from the basidiomycete Pleurotus ostreatus, assembles into a transmembrane pore complex. Here, we cloned complementary and genomic DNAs encoding pleurotolysin, and studied pore-forming properties of recombinant proteins. The genomic regions encoding pleurotolysin A and B contained two and eight introns, respectively, and putative promoter sequences. The complementary DNA (cDNA) for pleurotolysin A encoded 138 amino acid residues, and the predicted product was identical with natural pleurotolysin A, except for the presence of the first methionine. Recombinant pleurotolysin A lacking the first methionine was purified as a 17-kDa protein with sphingomyelin-binding activity. The cDNA for pleurotolysin B encoded a precursor consisting of 523 amino acid residues, of which N-terminal 48 amino acid residues were absent in natural pleurotolysin B. Mature and precursor forms of pleurotolysin B were expressed as insoluble 59- and 63-kDa proteins, respectively, which were unfolded with 8 M urea and refolded by 100-fold dilution with 10 mM Tris-HCl buffer, pH 8.5. Although neither recombinant pleurotolysin A nor B alone was hemolytically active at higher concentrations of up to 100 mg/ml, they cooperatively assembled into a membrane pore complex on human erythrocytes and lysed the cell as efficiently as the natural proteins at nanomolar concentrations. In contrast, the precursor of pleurotolysin B was much less hemolytically active than mature pleurotolysin B in the presence of pleurotolysin A.     

Isolation of a cDNA encoding the adenovirus E1A enhancer binding protein: a new human member of the ets oncogene family.

The cDNA encoding adenovirus E1A enhancer-binding protein E1A-F was isolated by screening a HeLa cell lambda gt11 expression library for E1A-F site-specific DNA binding. One cDNA clone produced recombinant E1A-F protein with the same DNA binding specificity as that endogenous to HeLa cells. Sequence analysis of the cDNA showed homology with the ETS-domain, a region required for sequence-specific DNA binding and common to all ets oncogene members. Analysis of the longest cDNA revealed about a 94% identity in amino acids between human E1A-F and mouse PEA3 (polyomavirus enhancer activator 3), a recently characterized ets oncogene member. E1A-F was encoded by a 2.5kb mRNA in HeLa cells, which was found to increase during the early period of adenovirus infection. In contrast, ets-2 mRNA was significantly reduced in infected HeLa cells. The results indicate that E1A enhancer binding protein E1A-F is a member of the ets oncogene family and is probably a human homologue of mouse PEA3.     

Outer membrane of Salmonella typhimurium. Identification of proteins exposed on cell surface.

Proteins exposed on the outer surface of the outer membrane of Salmonella typhimurium were identified by reacting intact cells with a covalent labeling reagent. Since the outer membrane permitted the free diffusion of small hydrophilic molecules, we used a macromolecular reagent, CNBr-activated dextran, as the non-penetrating labeling agent. We also used a mutant producing a lipopolysaccharide with a very short (i.e. hexasaccharide) carbohydrate chain, in order to avoid steric hindrance by the carbohydrates on membrane surface. Results showed that out of the four "major" proteins of molecular weight around 35 000, three were exposed, and that at least six other proteins were also exposed on cell surface. Only two or three outer membrane proteins consistently did not react with the reagent in intact cells.     

Phylogenetic relationships of the benign Theileria species in cattle and Asian buffalo based on the major piroplasm surface protein (p33/34) gene sequences.

In order to examine the taxonomic relationship of Theileria sp. of Asian buffalo to the benign Theileria spp. of cattle, we sequenced and compared the major piroplasm protein (p33/34) genes of these parasites. The two consensus sequences determined for the buffalo parasite were of the same length (852 bp) and showed >80% identity with the sequences of the homologous genes (849 bp) in the cattle parasites. Alignment of the inferred aa sequences with those of Theileria sergenti and Theileria buffeli predicted that there is an insertion of a single residue at the N-terminus in the inferred polypeptide of the buffalo parasite. Phylogenetic analyses based on the aa sequences suggested that Theileria sp. of the Asian buffalo should be classified within the benign Theileria parasite group as a separate species from the cattle parasites. Based on this, we propose a rearrangement of the currently used classification for the benign Theileria species in cattle and Asian buffalo.     

Gene cloning and molecular characterization of lysine decarboxylase from Selenomonas ruminantium delineate its evolutionary relationship to ornithine decarboxylases from eukaryotes

Lysine decarboxylase (LDC; EC 4.1.1.18) from Selenomonas ruminantium comprises two identical monomeric subunits of 43 kDa and has decarboxylating activities toward both L-lysine and L-ornithine with similar K(m) and V(max) values (Y. Takatsuka, M. Onoda, T. Sugiyama, K. Muramoto, T. Tomita, and Y. Kamio, Biosci. Biotechnol. Biochem. 62:1063-1069, 1999). Here, the LDC-encoding gene (ldc) of this bacterium was cloned and characterized. DNA sequencing analysis revealed that the amino acid sequence of S. ruminantium LDC is 35% identical to those of eukaryotic ornithine decarboxylases (ODCs; EC 4.1.1.17), including the mouse, Saccharomyces cerevisiae, Neurospora crassa, Trypanosoma brucei, and Caenorhabditis elegans enzymes. In addition, 26 amino acid residues, K69, D88, E94, D134, R154, K169, H197, D233, G235, G236, G237, F238, E274, G276, R277, Y278, K294, Y323, Y331, D332, C360, D361, D364, G387, Y389, and F397 (mouse ODC numbering), all of which are implicated in the formation of the pyridoxal phosphate-binding domain and the substrate-binding domain and in dimer stabilization with the eukaryotic ODCs, were also conserved in S. ruminantium LDC. Computer analysis of the putative secondary structure of S. ruminantium LDC showed that it is approximately 70% identical to that of mouse ODC. We identified five amino acid residues, A44, G45, V46, P54, and S322, within the LDC catalytic domain that confer decarboxylase activities toward both L-lysine and L-ornithine with a substrate specificity ratio of 0.83 (defined as the k(cat)/K(m) ratio obtained with L-ornithine relative to that obtained with L-lysine). We have succeeded in converting S. ruminantium LDC to form with a substrate specificity ratio of 58 (70 times that of wild-type LDC) by constructing a mutant protein, A44V/G45T/V46P/P54D/S322A. In this study, we also showed that G350 is a crucial residue for stabilization of the dimer in S. ruminantium LDC.     

An iron-binding protein,Dpr, from Streptococcus mutans prevents iron-dependent hydroxyl radical formation in vitro

The dpr gene is an antioxidant gene which was isolated from the Streptococcus mutans chromosome by its ability to complement an alkyl hydroperoxide reductase-deficient mutant of Escherichia coli, and it was proven to play an indispensable role in oxygen tolerance in S. mutans. Here, we purified the 20-kDa dpr gene product, Dpr, from a crude extract of S. mutans as an iron-binding protein and found that Dpr formed a spherical oligomer about 9 nm in diameter. Molecular weight determinations of Dpr in solution by analytical ultracentrifugation and light-scattering analyses gave values of 223,000 to 292,000, consistent with a subunit composition of 11.5 to 15 subunits per molecule. The purified Dpr contained iron and zinc atoms and had an ability to incorporate up to 480 iron and 11.2 zinc atoms per molecule. Unlike E. coli Dps and two other members of the Dps family, Dpr was unable to bind DNA. One hundred nanomolar Dpr prevented by more than 90% the formation of hydroxyl radical generated by 10 microM iron(II) salt in vitro. The data shown in this study indicate that Dpr may act as a ferritin-like iron-binding protein in S. mutans and may allow this catalase- and heme-peroxidase-deficient bacterium to grow under air by limiting the iron-catalyzed Fenton reaction.     

The third molecule associated with interleukin 2 receptor alpha and beta chain.

It is known that the affinity cross-linking study of the human high-affinity Interleukin 2 (IL-2) receptor reveals triplet bands consisting of 70 kDa alpha chain(Tac)-IL-2 and the 90/80 kDa doublet. We found the cell lines lacking the lower band of the doublet in spite of the expression of both alpha and beta chains. No IL-2 binding was detectable in the presence of anti-Tac antibody in these cells. Immunoprecipitation from the cell extract of [125 I] IL-2-cross-linked T cells with anti-beta chain polyclonal IgG detected the upper band, but not lower band of the doublet. These data suggest that the lower band of the doublet represents an unknown IL-2-binding protein (p65) distinct from the beta chain and this molecule may be involved in the intermediate-affinity IL-2 binding together with the beta chain.