Modulation of epothilone analog production through media design

Recently, the epothilone polyketide synthase (PKS) was successfully introduced into a heterologous production host for the large-scale production of epothilone D. We have found that at least three other epothilones can also be produced as the major fermentation product of this recombinant strain by supplementation of specific substrates to the production media. Addition of acetate or propionate to the media results in modulation of the epothilone D:C ratio, whereas addition of l-serine with either acetate or propionate yields epothilone H₁ or H₂ as the major product. This strategy permits production of at least four novel epothilones by culturing a single host with a genetically modified epothilone PKS in various media. Journal of Industrial Microbiology & Biotechnology (2002) 28, 17–20 DOI: 10.1038/sj/jim/7000209 Received 20 June 2001/ Accepted in revised form 03 September 2001     

Japanese juvenile retinoschisis is caused by mutations of the XLRS1 gene

We investigated the XLRS1 gene in Japanese patients with retinoschisis (RS). All exons of the XLRS1 gene were sequenced in 14 males, including a pair of monozygotic twins, from 11 individual families with RS and five of their mothers who are asymptomatic but diagnosed as carriers. Six kinds of missense mutations and a nonsense mutation, including six novel mutations, were detected in all 14 patients and carriers. Mutations in the XLRS1 gene are also responsible for RS in non-Caucasian patients. Most Japanese RS cases are caused by an XLRS1 gene defect. A novel mutation, Glu72Lys, was found in four families, suggesting a common mutation in the Japanese population. Clinical features of RS patients with both the Glu72Lys and Pro193Leu mutations indicate that a genotype–phenotype correlation is not recognized in RS. Received: 12 January 1998 / Accepted: 21 March 1998     

Fv-1 determinants in xenotropic murine leukemia viruses studied with biological assay systems: Isolation of xenotropic virus with N-tropic Fv-1 activity in the cryptic form.

By a biological assay system using phenotypically mixed ecotropic and xenotropic murine leukemia viruses, we investigated whether in the virions of a xenotropic virus there is N- or B-tropic Fv-1 determinant in active form. The existence of N-tropic Fv-1 determinant was demonstrated in SL-XT-1 xenotropic virus isolated from the spleen of a 3-month-old SL mouse, and the N-tropic Fv-1 tropism was confirmed by analysis of the phenotypically mixed viruses harvested from clonal SC-1 cells doubly infected with the SL-XT-1 and B-tropic ecotropic viruses. However, neither N- nor B-tropic Fv-1 determinant was demonstrated in any xenotropic viruses isolated from embryo cells of BALB/c, NZB, or DBA/2 mice, or Cas E #1-IU, and xenotropic-like virus isolated from a wild mouse.     

Chemical constituents and antioxidant activity of Mallotus roxburghianus leaves

Mallotus roxburghianus is used in the traditional medicine in North-Eastern India, but previously no work has been done on the identification of bioactive compounds. Two new compounds, 3-(1-C-beta-D-glucopyranosyl)-2,6-dihydroxy-5-methoxybenzoic acid (6) and 2,4,8,9,10-pentahydroxy-3,7-dimethoxyanthracene-6-O-beta-D-rhamnopyranoside (7) together with beta-sitosterol (1), stigmasterol (2), betulinic acid (3), 4-hydroxybenzoic acid (4), beta-sitosterol-beta-D-glucoside (5), and bergenin (8) were isolated and identified from the leaves of M. roxburghianus. The chloroform soluble portion of the alcoholic extract of leaf, and compounds 3, 6, 7, and 8 exhibited encouraging antioxidant activities.     

Induction of apoptosis in placentas of pregnant mice exposed to lipopolysaccharides: possible involvement of Fas/Fas ligand system

To explore the pathogenesis in placental dysfunction and abruptio placentae, we analyzed the occurrence of placental cell apoptosis and the role of Fas and Fas ligand (L) in that process in an inflammatory placental dysfunction model of pregnant mice, using lipopolysaccharides (LPS). In the present study, Day 13 pregnant mice were injected i.p. with LPS (50 microg/kg) or saline as a control, and the placentas were isolated at various time points after the injection. Analysis of the isolated DNA in agarose-gel electrophoresis revealed a typical ladder pattern of bands consisting of 180-200 base pairs (bp), which is regarded as a hallmark of apoptosis. The intensity of the bands increased time-dependently, reaching a maximum level at 12 h after LPS injection. In accord with the biochemical data, histochemical analysis using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) revealed that nuclei positive for double-stranded DNA breaks were found in decidua, diploid trophoblasts in the basal zone, and spongiotrophoblasts. The number of positive nuclei was maximized at 12 h after LPS injection. As a next step, we investigated the possible involvement of Fas and Fas L in the induction of apoptosis of the placental cells after LPS injection. Western blot analysis indicated that LPS increased the expression of Fas and Fas L in the placenta by about 4-fold at 12 h and 18 h, respectively, after injection. The cells expressing Fas and Fas L were identified, using immunohistochemistry and nonradioactive in situ hybridization, as decidua, diploid trophoblasts in the basal zone, and spongiotrophoblasts. Furthermore, when the expression of 4-hydroxy-2-nonenal (HNE)-modified proteins was assessed to evaluate the relation of oxidative stress elicited by LPS to the induction of apoptosis, once again decidua, diploid trophoblasts in the basal zone, and spongiotrophoblasts were positive. Therefore, the placental dysfunction by LPS may be brought about by the Fas-mediated apoptosis of various placental cells in a paracrine/autocrine fashion, possibly under the influence of oxidative stress.     

Structure of the E.coli aspartate transcarbamoylase trapped in the middle of the catalytic cycle

Snapshots of the catalytic cycle of the allosteric enzyme aspartate transcarbamoylase have been obtained via X-ray crystallography. The enzyme in the high-activity high-affinity R state contains two catalytic chains in the asymmetric unit that are different. The active site in one chain is empty, while the active site in the other chain contains an analog of the first substrate to bind in the ordered mechanism of the reaction. Small angle X-ray scattering shows that once the enzyme is converted to the R state, by substrate binding, the enzyme remains in the R state until substrates are exhausted. Thus, this structure represents the active form of the enzyme trapped at two different stages in the catalytic cycle, before the substrates bind (or after the products are released), and after the first substrate binds. Opening and closing of the catalytic chain domains explains how the catalytic cycle occurs while the enzyme remains globally in the R-quaternary structure.     

Green, herbicide-resistant plants by particle inflow gun-mediated gene transfer to diploid bahiagrass (Paspalum notatum)

We have established an efficient particle-bombardment transformation protocol for the diploid non-apomictic genotype of the warm season forage crop Paspalum notatum (bahiagrass). A vector containing a herbicide resistance gene (bar) together with the GUS reporter gene was used in transformation experiments. The bar gene confers resistance to the herbicide bialaphos. An improved culture system, highly regenerative callus, dense in compact polyembryogenic clusters, was produced on medium with a high CuSO4 content at elevated temperature. Target tissue (360 calli) produced under these conditions yielded 52 rooted plants on herbicide-containing medium, and 22 of these plants were PCR-positive. DNA gel blot analysis revealed a copy number of 1-5 for the GUS gene in different independent transformants. There was no correlation between copy number and GUS activity. While conventional cultures yielded exclusively albino plants on herbicide-containing medium, improved culture conditions for the target tissue resulted in the recovery of 100% green transgenic plants. All green herbicide-resistant regenerants were morphological normal and fertile.     

Synthesis of digalactosyl diacylglycerols and their structure-inhibitory activity on human lanosterol synthase

Digalactosyl and monogalactocyl diacylglycerols (DGDG and MGDG), which were identified as anti-hyperlipemia active components in Colocasia esculenta (Taro), were synthesized. The inhibitory activity of DGDG, MGDG and related compounds on human lanosterol synthase was evaluated as anti-hyperlipemic activity. DGDG with two myristoyl groups at both sn-1 and sn-2 positions and with an oleoyl group at the sn-1 position showed the most potent activity.     

Crystal structure of cold-active protein-tyrosine phosphatase from a psychrophile, Shewanella sp

The cold-active protein-tyrosine phosphatase (CAPTPase) of a psychrophile, Shewanella sp., shows high catalytic activity below 20 degrees C. The catalytic residue of CAPTPase is histidine, as opposed to the cysteine of known protein-tyrosine phosphatases (PTPases), and the enzyme protein has three amino acid sequences, Asp-Xaa-His, Gly-Asp-Xaa-Xaa-Asp-Arg and Gly-Asn-His-Glu, that are observed in many protein-serine/threonine phosphatases (PS/TPases). We have determined the crystal structures of CAPTPase at 1.82 angstroms and the enzyme bound with a phosphate ion at 1.90 angstroms resolution using X-ray crystallography and the multiple isomorphous replacement method. The final refined models are comprised of 331 amino acid residues, two metal ions, 447 water molecules, and an acetate or phosphate ion in an asymmetric unit. The enzyme protein consists of three beta-sheets, termed Sheet I, Sheet I', and Sheet II, and 14 alpha-helices. The CAPTPase has a different overall structure from known protein-tyrosine phosphatases. The arrangement of two metal ions, a phosphate ion and the adjacent amino acid residues in the catalytic site of CAPTPase is identical to that of PS/TPases. Thus, it was confirmed that the CAPTPase was a novel PTPase with a conformation similar to the catalytic site of PS/TPase. We speculate that the hydrophobic moiety around the catalytic residue of CAPTPase might play an important role in eliciting high activity at low temperature.