Morfeldt E, Janzon L, Arvidson S, Löfdahl S
Department of Bacteriology, National Bacteriological Laboratory, Stockholm, Sweden.
Mol Gen Genet. 1988 Mar;211(3):435-40. doi: 10.1007/BF00425697.
Insertion of the erythromycin resistance transposon Tn551 into a single site of the Staphylococcus aureus chromosome resulted in decreased production of alpha-toxin, serine and metallo-proteinases and several other extracellular proteins and a simultaneous increase in the production of protein A. The site of insertion, designated exp, was separate from the structural gene for alpha-toxin and protein A. Hybridization analysis showed that the effect of the insertional mutation on the expression of the alpha-toxin and protein A was at the level of transcription. The chromosomal DNA flanking the transposon and the corresponding DNA of the wild-type strain was cloned in Escherichia coli. Northern blot hybridization experiments revealed that the exp locus codes for a major RNA of approximately 3.5 kb. This RNA was not found in the insertional mutant nor in a spontaneous exp mutant. A map of the exp locus constructed by Northern blot and restriction enzyme analysis showed that the insertional mutation was located in the middle of the coding sequence of the 3.5 kb RNA. The insertional mutant was reverted to wild type by inserting a recombinant plasmid containing most of the coding sequence of the 3.5 kb RNA.
将红霉素抗性转座子Tn551插入金黄色葡萄球菌染色体的单个位点，导致α-毒素、丝氨酸蛋白酶和金属蛋白酶以及其他几种细胞外蛋白的产量降低，同时蛋白A的产量增加。插入位点命名为exp，与α-毒素和蛋白A的结构基因分开。杂交分析表明，插入突变对α-毒素和蛋白A表达的影响发生在转录水平。转座子两侧的染色体DNA和野生型菌株的相应DNA被克隆到大肠杆菌中。Northern印迹杂交实验表明，exp位点编码一种约3.5 kb的主要RNA。在插入突变体和自发exp突变体中均未发现这种RNA。通过Northern印迹和限制性酶分析构建的exp位点图谱表明，插入突变位于3.5 kb RNA编码序列的中间。通过插入含有3.5 kb RNA大部分编码序列的重组质粒，插入突变体恢复为野生型。
