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从葡萄糖异构酶产生菌──玫瑰红链霉菌336中分离得到质粒pSR336。经电泳检测和电镜观察证实,存在共价闭合超螺旋和开环两种分子构型,分子量约为6.35kb,拷贝数约为130。采用高温(40℃),吖啶橙、溴化乙锭和SDS等物理、化学因素消除pSR336,均未获得质粒消除株,表明pSR336质粒是非常稳定的。用变铅青链霉菌TK21作受体,进行平皿杂交以检测pSR336的接合转移能力,未观察到麻点(pock)的形成。用HindⅢ分别酶切pSR336和pIJ486,连接得到一个嵌合质粒pIR30,检测玫瑰红链霉 相似文献
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碳源和氮源对玫瑰栗色链霉菌No.336产葡萄糖异构酶的影响 总被引:1,自引:0,他引:1
玫瑰粟色链霉菌(Streptomyces rosecocastaneus) No. 336变异株对碳源或氮源的利用及其和产葡萄糖异构酶的关系,用半合成培养基进行了摇瓶液体培养试验。测定以15种单精和糖醇、8种寡糖和5种多糖作为碳源,6种含氮化合物作为氮源对菌的生长和产酶的影响。证明N。.336菌株除利用L一阿拉伯糖和D二木糖等五碳糖作为碳源外,也能利用D一葡萄糖等六碳糖作为碳源和能源。糖醇对酶的形成或无明显影响,或有抑制作用。在供试的氮源中,玉米浆和酵母膏对产酶的影响明显优于蛋白胨,该菌几乎不能以无帆氮化合物或乙酸镶作为唯一的氮源。C/N比的试验表明,2:1、1:1或3:1的培养基组成有利于葡萄糖异梅酶的形成,提高氮素含量虽能促进菌的生长,但对产酶不利。以麦麸水解液和玉米浆为主要成分的培养基有利于No.336菌株的生长和产酶,每毫升培养液的酶活力在180单位以上。 相似文献
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López-Hernández GY Biaggi-Labiosa NM Torres-Cintrón A Ortiz-Acevedo A Lasalde-Dominicci JA 《Cellular and molecular neurobiology》2009,29(1):41-53
Phosphorylation of the nicotinic acetylcholine receptor (nAChR) is believed to play a critical role in its nicotine-induced
desensitization and up-regulation. We examined the contribution of a consensus PKC site in the α4 M3/M4 intracellular loop
(α4S336) on the desensitization and up-regulation of α4β2 nAChRs expressed in oocytes. Position α4S336 was replaced with either
alanine to abolish potential phosphorylation at this site or with aspartic acid to mimic phosphorylation at this same site.
Mutations α4S336A and α4S336D displayed a threefold increase in the ACh-induced response and an increase in ACh EC50. Epibatidine binding revealed a three and sevenfold increase in surface expression for the α4S336A and α4S336D mutations,
respectively, relative to wild-type, therefore, both mutations enhanced expression of the α4β2 nAChR. Interestingly, the EC50’s and peak currents for nicotine activation remained unaffected in both mutants. Both mutations abolished the nicotine-induced
up-regulation that is normally observed in the wild-type. The present data suggest that adding or removing a negative charge
at this phosphorylation site cannot be explained by a simple straightforward on-and-off mechanism; rather a more complex mechanism(s)
may govern the functional expression of the α4β2 nAChR. Along the same line, our data support the idea that phosphorylation
at multiple consensus sites in the α4 subunit could play a remarkable role on the regulation of the functional expression
of the α4β2 nAChR. 相似文献
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The mitochondrial translational machinery allows the genes encoded by mitochondrial DNA (mtDNA) to be translated in situ. Mitochondrial translation requires a number of nucleus-encoded protein factors, some of which have been found to carry mutations in patients affected by mitochondrial encephalomyopathies. We have previously described the first, and so far only, mutation in the mitochondrial elongation factor Tu, mt-EFTu, in a baby girl with polycystic encephalopathy, micropolygyria, and leukodystrophic changes. Despite that the mutant mt-EFTu was present in normal amount in the patient's tissues, mitochondrial translation was severely reduced, determining multiple defects in the amount and activity of mtDNA-dependent respiratory chain complexes. By an in-vitro reconstructed translational system, we here provide evidence that the mutant mt-EFTu variant fails to bind to aminoacylated mitochondrial tRNAs, thus explaining the observed impairment of mitochondrial translation. This is the first analysis on the molecular mechanism of a mtDNA translation defect due to a nuclear gene mutation. 相似文献
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