Scott T N, Simon M I
Mol Gen Genet. 1982;188(2):313-21. doi: 10.1007/BF00332694.
Phase variation, the alternation of expression of flagellar antigens H1 and H2, in Salmonella typhimurium is mediated by site specific inversion of a 995 bp DNA segment of the chromosome. Hin, a protein encoded within the 995 bp segment, is thought to catalyze the recombination reaction between 14 bp inverted repeats flanking the 995 bp segment. By comparison of the relative rates of inversion of two different plasmids containing the H2 inversion segment flanked by different sequences, we conclude that the sequences adjacent to the inversion segment affect the rate of inversion. Homologous pairing of the repeats is important in H2 inversion since the orientation of the repeats on the host molecule(s) determines the result of the recombination reaction. The presence of the hin gene mediates the fusion of two plasmids when each contains one of the 14 bp repeat sequences. When the 14 bp sequences are direct repeats on a single molecule the sequence between them is deleted. These results support the hypothesis that the H2 inversion system functions by homologous, conservative, site specific recombination which is similar to the systems found associated with TnA transposons and temperate bacteriophage.
在鼠伤寒沙门氏菌中，鞭毛抗原H1和H2表达的交替变化即相变，是由染色体上一段995 bp的DNA片段的位点特异性倒位介导的。Hin是在995 bp片段内编码的一种蛋白质，被认为催化995 bp片段两侧14 bp反向重复序列之间的重组反应。通过比较两个含有侧翼为不同序列的H2倒位片段的不同质粒的相对倒位率，我们得出结论，与倒位片段相邻的序列会影响倒位率。重复序列的同源配对在H2倒位中很重要，因为重复序列在宿主分子上的方向决定了重组反应的结果。当每个质粒都含有14 bp重复序列之一时，hin基因的存在介导了两个质粒的融合。当14 bp序列在单个分子上为同向重复序列时，它们之间的序列会被删除。这些结果支持了这样一种假说，即H2倒位系统通过同源、保守、位点特异性重组发挥作用，这与与TnA转座子和温和噬菌体相关的系统类似。
