Seroreactivity and immunogenicity of Tp0965, a hypothetical membrane protein of Treponema pallidum / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Treponema pallidum (T. pallidum) subsp. pallidum is the causative agent of syphilis. Analysis of recombinant antigens of T. pallidum led to the identification of potential candidate antigens for vaccine development and syphilis serodiagnosis. Tp0965 was predicted to be a membrane fusion protein and was found to be reactive with infected human sera in previous studies, but the results were controversial. In this research, the antigenicity and immunoreactivity of recombinant protein Tp0965 were assessed.</p><p><b>METHODS</b>T. pallidum subsp. pallidum (Nichols strain) was propagated and isolated and the genomic DNA was extracted. The Tp0965 gene was amplified by polymerase chain reaction (PCR). Then the recombinant protein Tp0965 was expressed in Escherichia coli and purified by nickel-nitrilotriacetic acid (Ni-NTA) purification system. The reactivities of protein Tp0965 were examined by immunoblot analysis and indirect enzyme-linked immunosorbent assay. The antisera against protein Tp0965 were obtained by immune rabbits and the immunogenicity of antisera were detected by indirect enzyme-linked immunosorbent assay.</p><p><b>RESULTS</b>Recombinant protein Tp0965 was expressed successfully in vitro. Immunoblot assay showed that the recombinant protein Tp0965 could be recognized by human syphilitic sera of all stages. Indirect enzyme-linked immunosorbent assay showed there were only 4 of 74 human syphilitic sera that failed to show reactivity to recombinant antigen Tp0965, and lack of reactivity of Tp0965 to all 28 uninfected sera. A low titer of antiserum against Tp0965 in immune rabbits could be detected after the third time of immunization.</p><p><b>CONCLUSIONS</b>The recombinant antigen Tp0965 shows excellent sensitivity for the reactivity with sera from syphilitic individuals at all stages. The results also demonstrate a potential application for the serodiagnosis of syphilis.</p>

Study of a novel antiosteoporosis screening model targeted on cathepsin K / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To establish an effective assay to access the effects of natural products on cathepsin K for screening antiosteoporosis drugs.</p><p><b>METHODS</b>To obtain the purified cathepsin K, we cloned the target fragment from the mRNA of human osteosacoma cell line MG63 and demonstrated its correctness through DNA sequencing. Cathepsin K was expressed in a high amount in E. coli after IPTG induction, and was purified to near homogenetity through resolution and column purification. The specificity of the protein was shown by Western blotting experiment. The biological activity of the components in the fermentation broth was assayed by their inhibitory effects on cathepsin K and its analog papain.</p><p><b>RESULTS</b>With the inhibition of papain activity as a screen index, the fermentation samples of one thousand strains of fungi were tested and 9 strains among them showed strong inhibitory effects. The crude products of the fermentation broth were tested for their specific inhibitory effects on the purified human cathepsin K, the product of fungi 2358 shows the highest specificity against cathepsin K.</p><p><b>CONCLUSIONS</b>The compounds isolated from fungi 2358 show the highest biological activity and are worth further structure elucidation and function characterization.</p>

Establishment of gene transduction system in geldanamycin producer - Streptomyces hygroscopicus 17997 and its application for gene disruption experiment / 生物工程学报

Streptomyces hygroscopicus 17997 produces the antiviral and antitumor ansamycin antibiotic, geldanamycin. Studies on geldanamycin biosynthetic pathway will provide good tools for genetic manipulation of the antibiotic-producing strain to improve the productivity or to facilitate making novel geldanamycin analogs. The structural similarities between geldanamycin and ansamycins such as rifamycin or ansatrienin suggest that both geldanamycin and ansamycins has a closely related pathways of biosynthesis and that biosynthetic system for geldanamycin is similar to the one of type I polyketide synthase (PKS) enzyme system. To explore the possible PKS genes involved in geldanamycin biosynthesis, the degenerate primers were designed according to the conserved sequence of KS-AT region from erythromycin and oleandomycin type I PKS genes. Cosmids containing multiple PKS genes (pCGBK2,4,6,10,11,18) were obtained by hybridization with the PCR products, which were amplified from S. hygroscopisus 17997 genomic DNA. The designed primers above were used for PCR. Development of a Streptomyces temperate phage phiC31-derivative KC515( tsrR) transduction system was carried out for identification of cosmids containing the PKS gene related to biosynthesis of geldanamycin. Several factors, mainly the Ca2+ and Mg + concentrations in different culture media affecting the frequency of gene transfection, were optimized .Transfection efficiency could reach up to 10(3) /microg DNA on YMG medium supplemented with 10mmol/L MgSO4. Reversely, the transfection efficiency decreased when YMG medium was supplemented with 30mmol/L MgSO4. Gene transfection system based on the integration-defective phage KC515 had been established for S. hygroscopicus17997. Recombinant phages (ph111, 258, 287, 116, 105) were constructed by insertion of the homologous to PKS gene fragments into the KC515 phage vector. Gene disruption experiments were performed by transduction of recombinant phages into S. hygroscopicus 17997 genome, and disruption of geldanamycin production was observed as a result of homologous recombination between the cloned insert in recombinant phage and the S. hygroscopicus 17997 genome by integration. Thiostrepton resistant transductants were selected and integration event was analyzed by Southern hybridization. The fermentation broth extracts from five resistant transductants were analyzed by TLC and HPLC. The results showed that only G16 mutant failed to produce geldanamycin. This result showed that the integration of the insert DNA fragment in recombinant phage phl6 into the chromosome of S. hygroscopicus disrupted the expression of the geldanamycin biosynthetic genes. The original cosmid pCGBK10 containing this cloned insert was predicted to encode PKS genes in the geldanamycin biosynthesis. This study laid the foundation for cloning the PKS genes involved in geldanamycin biosynthetic gene cluster from S. hygroscopicus 17997.