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棕色固氮菌(Azotobacter vinelandii Lipmann)突变种UW3能在无Mo的无氨培养基中固氮生长,低浓度的Mn对UW3突变种生长有促进作用,从在Mn中生长的UW3菌体中分离得到的部分纯固氮酶组分Ⅰ蛋白含量有Mn和Fe原子(Fe/Mo/Mn为10.41:0.19:1.00)并有OP MoFe蛋白一半的还原乙炔和质子的活性。这种蛋白的吸收光谱和圆二色谱与MoFe蛋白存在明显的差异,含Mn蛋白的亚基分子量都与MoFe蛋白的α亚基相近。初步结果表明,这种含Mn蛋白可胡是一种固氮酶组分Ⅰ蛋白。 相似文献
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在合适的结晶条件下 ,从含Cr无氨培养基中生长的固氮菌 (AzotobactervinelandiiLipmann)突变种UW3 中纯化出的CrFe蛋白可从溶液中析出深棕色斜四棱柱晶体 ,晶体最大的两条对角线长度分别可达 0 .2 5mm和 0 .12mm。PEG 80 0 0、MgCl2 、NaCl、Tris和Hepes缓冲液的浓度及结晶方法等对该蛋白的出晶率、晶核数目、晶体大小和质量都有明显影响。CrFe蛋白结晶所需的上述化合物的最适浓度与在Mn中生长的固氮菌突变种UW3 的MnFe蛋白和缺失nifZ固氮菌突变种的ΔnifZMoFe蛋白结晶所需的最适浓度有所不同。结果表明 ,该蛋白晶体可能为CrFe蛋白的晶体 相似文献
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Oral Antibiotic Treatment of Mice Exacerbates the Disease Severity of Multiple Flavivirus Infections
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Spady TJ Shayya R Thackray VG Ehrensberger L Bailey JS Mellon PL 《Molecular endocrinology (Baltimore, Md.)》2004,18(4):925-940
Little is known about the molecular mechanisms of androgen regulation of the FSHbeta gene; however, studies suggest that it consists of a complex feedback loop that involves multiple mechanisms acting at both the level of the hypothalamus and the pituitary. In the present study, we address androgen regulation of the FSHbeta gene in immortalized gonadotrope cells and investigate the roles of activin and GnRH in androgen action. Using transient transfection assays in the FSHbeta-expressing mouse gonadotrope cell line, LbetaT2, we demonstrate that androgens stimulate expression of an ovine FSHbeta reporter gene in a dose-dependent manner. Mutation of either of two conserved androgen response elements at -245/-231 and -153/-139 within the proximal region of the ovine FSHbeta gene promoter abolishes this stimulation, and androgen receptor binds directly to the -244 ARE in vitro. Androgen induction of the FSHbeta reporter gene is also dependent upon the activin autocrine loop present in the LbetaT2 cells, as well as an activin-response element at -138/-124 of the FSHbeta gene. However, activin regulation of other genes remains unaffected by androgens. In addition, androgens stimulate expression of a mouse GnRH receptor reporter gene, and thus may indirectly augment the response of the FSHbeta gene to GnRH. Taken together, these data demonstrate that, in mouse gonadotropes, androgens act directly on the ovine FSHbeta gene to stimulate expression by a mechanism that is dependent upon activin, as well as acting indirectly, potentially through a second mechanism that may be dependent upon induction of GnRH receptor. 相似文献
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We have isolated the delta-globin gene of the New-World spider monkey,
Ateles geoffroyi, and compared its nucleotide sequence with those of other
primate delta- and beta-globin genes. Among primate delta-globin genes, the
rate of nonsynonymous substitutions is much less than the rate of
synonymous substitutions. This suggests that primate delta- globin genes
may remain under evolutionary conservation, perhaps because hemoglobin A2
has an as yet unknown physiological importance.
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