Yanofsky M F, Porter S G, Young C, Albright L M, Gordon M P, Nester E W
Cell. 1986 Nov 7;47(3):471-7. doi: 10.1016/0092-8674(86)90604-5.
Tumor formation by Agrobacterium tumefaciens involves the transfer and integration of a defined segment (T-DNA) of tumor-inducing (Ti) plasmid DNA into the plant nuclear genome. A set of plasmid genes outside the T-DNA, the vir genes, are thought to mediate the transfer process. We report here that the virD operon encodes a site-specific endonuclease that cleaves at a unique site within each of the 24 bp direct repeats that flank the T-DNA. The endonuclease function was further localized to the 5' end of this operon by demonstrating that cleavage does not occur in virD mutant strains of Agrobacterium and that the 5' end of the virD operon is sufficient to direct cleavage in E. coli. Analysis of nucleotide sequence and protein data indicate that two proteins of 16.2 and 47.4 kd are involved.
根癌土壤杆菌诱导肿瘤形成涉及肿瘤诱导（Ti）质粒DNA特定片段（T-DNA）转移并整合到植物核基因组中。T-DNA之外的一组质粒基因，即vir基因，被认为介导了这一转移过程。我们在此报告，virD操纵子编码一种位点特异性内切核酸酶，该酶在T-DNA两侧24 bp直接重复序列中的每个独特位点进行切割。通过证明在根癌土壤杆菌的virD突变菌株中不发生切割，且virD操纵子的5'端足以在大肠杆菌中指导切割，进一步将内切核酸酶功能定位到该操纵子的5'端。核苷酸序列和蛋白质数据分析表明，涉及两种分别为16.2 kd和47.4 kd的蛋白质。
