REPEATED SEQUENCE SIMILAR TO INSERTION ELEMENTS IN THE RHIZOBIUM ASTRAGALI GENOME
紫云英根瘤菌基因组中存在有类似IS因子的DNA重复顺序

A DNA repeated sequence has been found in the Rhizobium astragali genome designated as RSRa. It is repeated 4 - 5 times in the genome. One copy of it is located upstream of nifH. By using of a 1.25kb Pvul fragment as a specific probe, homologous RSRa was detected in different strains of R. astragali and also in one strain of R. leguminosarum PRE tested. Nucleotide sequence analysis revealed that RSRa possesses the structural characteristics of prokaryotic insertion sequence elements. RSRa is 1468 bp in length with 398 bp terminal inverted repeats. A large open reading frame, putatively the gene coding for transponase, was found in the RSRa. Comparison of the putative protein encoded with sequences derived from the GeneBank and SWISS-Prot datebase showed significant similarity between the putative transponase encoded by RSRa and that encoded by E. coli IS903.