Segal G, Ron E Z
Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Israel.
J Bacteriol. 1995 Oct;177(20):5952-8. doi: 10.1128/jb.177.20.5952-5958.1995.
The dnaKJ operon of Agrobacterium tumefaciens was cloned and sequenced and was found to be highly homologous to previously analyzed dnaKJ operons. Transcription of this operon in A. tumefaciens was stimulated by heat shock as well as by exposure to ethanol and hydrogen peroxide. There were two transcripts representing the dnaKJ operon: one containing the dnaK and dnaJ genes and the second containing only the dnaK gene. Primer extension analysis indicated that transcription started from the same site in heat-shocked cells and in untreated cells. The upstream regulatory region of the dnaKJ operon of A. tumefaciens does not contain the highly conserved inverted repeat sequence previously found in the groESL operon of this bacterium, as well as in many other groE and dnaK operons. Sequence analysis of the promoter region of several groESL and dnaK operons from alpha-purple proteobacteria indicates the existence of a putative promoter sequence different from the known consensus promoter sequences recognized by the Escherichia coli vegetative or heat shock sigma factor. This promoter may constitute the heat shock promoter of these alpha-purple proteobacteria.
根癌土壤杆菌的dnaKJ操纵子被克隆并测序，发现它与先前分析的dnaKJ操纵子高度同源。该操纵子在根癌土壤杆菌中的转录受热激以及暴露于乙醇和过氧化氢的刺激。有两种转录本代表dnaKJ操纵子：一种包含dnaK和dnaJ基因，另一种仅包含dnaK基因。引物延伸分析表明，转录在热激细胞和未处理细胞中从同一位置开始。根癌土壤杆菌dnaKJ操纵子的上游调控区不包含先前在该细菌的groESL操纵子以及许多其他groE和dnaK操纵子中发现的高度保守的反向重复序列。对来自α-紫色变形菌的几个groESL和dnaK操纵子的启动子区域进行序列分析表明，存在一个推定的启动子序列，该序列不同于大肠杆菌营养型或热激σ因子识别的已知共有启动子序列。这个启动子可能构成这些α-紫色变形菌的热激启动子。
