National Changhua University of Education Institutional Repository : Item 987654321/8982
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题名: Sequence Analysis of a DNA Fragment from Buchnera Aphidicola (an endosymbiont of aphids) Containing Genes Homologous to dnaG, rpoD, cysE, and secB
作者: Chi-Yung Lai;Paul Baumann
贡献者: 生物系
关键词: Schizaphis graminum;molecular evolution;DNA primase;sigma factor;serine acetyltransferase;protein secretion
日期: 1992-09
上传时间: 2011-05-16T07:38:44Z
出版者: Elsevier Science
摘要: The aphid, Schizaphis graminum, contains a prokaryotic, obligately intracellular endosymbiont, Buchnera aphidicola, which is necessary for the survival of the host. A recent study of Bu. aphidicola 16S rRNA has indicated that it is a member of the gamma-3 subdivision of the eubacterial class, Proteobacteria, which includes Escherichia coli. In order to further characterize the endosymbiont and establish its similarity to free-living eubacteria and/or organelles, we have cloned and sequenced a 4534-bp DNA fragment containing dnaG-rpoD-cysE-secB. The deduced amino acid (aa) sequence identity to the homologous E. coli proteins ranged from 47 to 80%. The close proximity of the pair, dnaG-rpoD, to the pair, cysE-secB, on the Bu. aphidicola DNA, differed from E. coli, in which these two pairs of genes are 14 min apart on the bacterial chromosome. The results of past physiological studies of the endosymbiont were consistent with the presence and function of DNA primase (DnaG), σ factor (RpoD) and components of the secretory system (SecB). Comparison of the deduced aa sequence of Bu. aphidicola CysE (serine acetyltransferase, a key allosterically regulated enzyme in cysteine biosynthesis) with the E. coli wild-type enzyme and a mutant defective in feedback inhibition suggested that the endosymbiont CysE may not be regulated. By analogy with E. coli, the lack of feedback inhibition may lead to overproduction of cysteine by the endosymbiont. The results of this and previous investigations indicate that Bu. aphidicola has many of the properties of free-living bacteria and not of organelles.
關聯: Gene, 119(1):113-118
显示于类别:[生物技術研究所] 期刊論文

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