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在紫云英根瘤菌(Rhizobium astragali)的基因组中存在有DNA重复顺序(RSRa)。它在Ra159的基因组中重复4～5次,其中一个拷贝位于nifH基因的上游。以1.25kbPvul片段作探针,在其他紫云英根瘤菌菌株及豌豆根瘤菌RI PRE中也都检测到与RSRa同源的DNA片段。序列测定的结果表明RSRa其结构类似于IS因子,具有原核插入顺序的一些特点。RSRa全长1468bp,在RSRa的两个末端具有反向重复顺序,RSRa中有一个大的开放阅读框架(ORF)。由ORF推定的蛋白与大肠杆菌插入顺序IS903推定的转座酶有较高的同源性。
There is a DNA repeat sequence (RSRa) in the genome of Rhizobium astragali. It is repeated 4 to 5 times in the genome of Ra159, one copy of which is located upstream of the nifH gene. A 1.25kbPvul fragment was used as a probe and a DNA fragment homologous to RSRa was also detected in other strains of Rhodotoriria viridis and RI PRE. The results of sequencing showed that RSRa is similar in structure to IS factor and has some characteristics of prokaryotic insertion sequence. RSRa is 1468 bp in length with an inverted repeat sequence at both ends of RSRa and a large open reading frame (ORF) in RSRa. The putative protein from the ORF has high homology with the putative transposase from Escherichia coli insertion sequence IS903.