Close T J, Tait R C, Rempel H C, Hirooka T, Kim L, Kado C I
J Bacteriol. 1987 Jun;169(6):2336-44. doi: 10.1128/jb.169.6.2336-2344.1987.
The virC (formerly bak) complementation group of the nopaline-type Ti plasmid pTiC58 encodes two proteins, VirC1 and VirC2. According to the primary structure of the polypeptides predicted by the nucleotide sequence, VirC1 is composed of 231 amino acids with a total molecular mass of 25.5 kilodaltons, and VirC2 is composed of 202 amino acids with a molecular mass of 22.1 kilodaltons. The pTiC58 VirC1 and VirC2 polypeptides are equal in length to VirC1 and VirC2 of the octopine-type plasmid pTiA6NC. VirC1 proteins of pTiC58 and pTiA6NC are identical at 202 (87.4%) of the amino acid residues, and this homology is distributed fairly evenly throughout the protein. VirC2 identities occur at 142 residues (70.3%), but fall predominantly into two blocks of higher homology (84.6 and 78.5%) separated by a 41-residue segment of much lower homology (29.3%). Mutations in virC resulted in attenuated virulence on all hosts tested, the severity of attenuation varying markedly depending on the type of plant inoculated. For example, the attenuation was more pronounced on Kalanchoe than on sunflower or jimson weed. Virulence was restored to normal on all hosts by in-trans complementation with corresponding nonmutant DNA fragments of pTiC58 or of the octopine-type plasmid pTi15955. Two oligopeptides from within the predicted pTiC58 VirC1 polypeptide were synthesized and used to raise antibodies. These antibodies were used to detect the VirC1 product of both pTiC58 and pTi15955. In both cases, virC was expressed constitutively in the Agrobacterium tumefaciens ros mutant. The homology between virC genes of octopine- and nopaline-type Ti plasmids thus includes a conservation of genetic regulatory control mechanisms as well as considerable conservation of the primary structure of the protein products.
胭脂碱型Ti质粒pTiC58的virC（以前称为bak）互补群编码两种蛋白质，即VirC1和VirC2。根据核苷酸序列预测的多肽一级结构，VirC1由231个氨基酸组成，总分子量为25.5千道尔顿，VirC2由202个氨基酸组成，分子量为22.1千道尔顿。pTiC58的VirC1和VirC2多肽与章鱼碱型质粒pTiA6NC的VirC1和VirC2长度相等。pTiC58和pTiA6NC的VirC1蛋白在202个（87.4%）氨基酸残基处相同，这种同源性在整个蛋白质中分布相当均匀。VirC2的同源性出现在142个残基处（70.3%），但主要集中在两个同源性较高的区域（84.6%和78.5%），中间由一个同源性低得多的41个残基片段（29.3%）隔开。virC中的突变导致在所有测试宿主上的毒力减弱，但减弱的严重程度因接种植物的类型而异。例如，在长寿花上的减弱比在向日葵或曼陀罗上更明显。通过用pTiC58或章鱼碱型质粒pTi15955的相应非突变DNA片段进行反式互补，所有宿主上的毒力都恢复到了正常水平。合成了预测的pTiC58 VirC1多肽中的两个寡肽并用于制备抗体。这些抗体用于检测pTiC58和pTi15955的VirC1产物。在这两种情况下，virC在根癌土壤杆菌ros突变体中组成型表达。因此，章鱼碱型和胭脂碱型Ti质粒的virC基因之间的同源性包括遗传调控机制的保守以及蛋白质产物一级结构的相当程度的保守。
