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对互补紫云英根瘤菌Ｅｘｏ－Ｎｄｖ－Ｆｉｘ－变种的２．６ｋｂＤＮＡ片段进行序列测定。分析结果表明，该片段内存在一个完整的阅读框架（ＯＲＦ）ｅｘｏ１。ｅｘｏ１编码３４０个氨基酸，为细胞质蛋白。Ｅｘｏ１蛋白序列与苜蓿根瘤菌的糖基转移酶ＥｘｏＵ有较强的同源性。利用启动子检测质粒，分析ｅｘｏ１基因的表达，发现在ｅｘｏ１基因上有两个启动子活性区段，Ｐｅｘｏ１ａ位于基因前端，Ｐｅｘｏ１ｂ位于基因中间。Ｐｅｘｏ１ａ很可能包含了ｅｘｏ１基因的启动子。
The sequence of 2.6kb DNA fragment of Rhizobium fredii Exo-Ndv-Fix-variant was sequenced. The analysis showed that there is a complete reading frame (ORF) exo1 in this fragment. Exo1 encodes 340 amino acids, a cytoplasmic protein. Exo1 protein sequence and alfalfa Rhizobium glycosyltransferase ExoU have strong homology. Plasmids were detected with a promoter and the exo1 gene was analyzed for expression. Two exon 1 promoter segments were found, with Pexo1a at the front of the gene and Pexo1b at the middle of the gene. Pexo1a likely contains the exo1 gene promoter.