Winans S C, Allenza P, Stachel S E, McBride K E, Nester E W
Nucleic Acids Res. 1987 Jan 26;15(2):825-37. doi: 10.1093/nar/15.2.825.
The Agrobacterium tumefaciens Ti plasmid contains at least six transcriptional units (designated vir loci) which are essential for efficient crown gall tumorigenesis. Mutations in one of these loci, virE, result in a sharply attenuated virulence phenotype. In the present communication, we have analyzed the virE operon at the molecular level. This locus contains open reading frames coding for two hydrophilic proteins having molecular weights of approximately 7,000 daltons and 60,500 daltons. Using a maxicell strain of E. coli, we have visualized two proteins encoded by virE which correspond in size to these open reading frames. Analysis of codon usage of virE and seven other vir loci indicates that, in contrast to E. coli, all possible codons for a given amino acid are utilized at approximately the same frequency.
根癌土壤杆菌的Ti质粒至少包含六个转录单元（称为vir位点），这些对于有效的冠瘿瘤形成至关重要。这些位点之一virE中的突变会导致毒力表型急剧减弱。在本通讯中，我们在分子水平上分析了virE操纵子。该位点包含编码两种亲水性蛋白质的开放阅读框，其分子量分别约为7000道尔顿和60500道尔顿。使用大肠杆菌的大细胞菌株，我们可视化了由virE编码的两种蛋白质，其大小与这些开放阅读框相对应。对virE和其他七个vir位点的密码子使用情况分析表明，与大肠杆菌不同，给定氨基酸的所有可能密码子的使用频率大致相同。
