Lereclus D, Ribier J, Klier A, Menou G, Lecadet M M
EMBO J. 1984 Nov;3(11):2561-7. doi: 10.1002/j.1460-2075.1984.tb02174.x.
A DNA segment (Th-sequence) has been found in several strains of Bacillus thuringiensis. This Th-sequence [3 megadaltons (Md)] induces adjacent deletions when it is located in the pAM beta 1 plasmid derived from Streptococcus faecalis. Electron microscopic examination of reannealed single strands of one plasmid (pMT9) carrying such a deletion revealed that the Th-sequence corresponds to a single-stranded loop (2.8 Md) bounded by a short double-stranded stem (less than 0.2 Md). Southern blotting experiments established that in B. thuringiensis the Th-sequence was generally located on the large plasmid which also harbours the gene coding for the delta-endotoxin (crystal protein). Hybridization and heteroduplex analysis of the extrachromosomal DNA from the berliner 1715 strain demonstrated that the crystal gene and the Th-sequence are located in close vicinity on a 42-Md plasmid and that they are separated by a 1.3-Md DNA segment. This DNA segment is repeated in inverted orientation, once immediately adjacent to the Th-sequence and once 1.8 Md beyond the crystal gene. A model for the organization of these DNA sequences inside a transposon-like structure is proposed.
在几种苏云金芽孢杆菌菌株中发现了一个DNA片段（Th序列）。当这个Th序列（3兆道尔顿）位于源自粪链球菌的pAMβ1质粒中时，会诱导相邻区域发生缺失。对携带这种缺失的一个质粒（pMT9）重新退火的单链进行电子显微镜检查发现，Th序列对应于一个由短双链茎（小于0.2兆道尔顿）界定的单链环（2.8兆道尔顿）。Southern印迹实验表明，在苏云金芽孢杆菌中，Th序列通常位于也携带编码δ-内毒素（晶体蛋白）基因的大质粒上。对berliner 1715菌株的染色体外DNA进行杂交和异源双链分析表明，晶体基因和Th序列位于一个42兆道尔顿质粒上的紧邻区域，它们被一个1.3兆道尔顿的DNA片段隔开。这个DNA片段以反向重复，一次紧邻Th序列，一次在晶体基因下游1.8兆道尔顿处。本文提出了一个关于这些DNA序列在转座子样结构内组织方式的模型。
