Kado Clarence I
Davis Crown Gall Group, University of California, One Shields Avenue, Davis, CA 95616, USA.
Plasmid. 2002 Nov;48(3):179-85. doi: 10.1016/s0147-619x(02)00116-6.
The chromosomal ros gene in Agrobacterium tumefaciens encodes a repressor of virulence and oncogenes that are located on a resident Ti plasmid. Mutational inactivation of ros de-represses the expression of the virC and virD operons, causing premature processing and accumulation of T-DNA molecules, and the premature expression of the oncogene, ipt, leading to the synthesis of cytokinin in the bacterium rather than in the plant host cell. Ros is a 15.5 kDa protein containing a novel "eukaryotic" C(2)H(2) zinc finger. Amino acid substitutions in the finger result in the loss of binding of Ros to the ros box, a 40 bp sequence within the operator of virC/D and ipt gene promoters; and the loss of binding of a zinc ion. The ros gene is highly conserved in members of the Rhizobiaceae. Evolutionary distance tree analyses revealed distant ties to the Japanese puffer fish, Fugu rupripes rather than to plants. Interestingly, ros homologues were found in microorganisms derived from marine sources, supporting the hypothesis that ros may have originated from a marine rather than a terrestrial organism.
根癌土壤杆菌中的染色体ros基因编码一种位于常驻Ti质粒上的毒力和致癌基因的阻遏物。ros的突变失活会解除virC和virD操纵子的表达抑制，导致T-DNA分子的过早加工和积累，以及致癌基因ipt的过早表达，从而导致细菌而非植物宿主细胞中细胞分裂素的合成。Ros是一种15.5 kDa的蛋白质，含有一个新型的“真核”C(2)H(2)锌指。锌指中的氨基酸取代导致Ros与ros框（virC/D和ipt基因启动子操纵区内的一个40 bp序列）的结合丧失，以及锌离子结合的丧失。ros基因在根瘤菌科成员中高度保守。进化距离树分析表明，它与日本河豚（红鳍东方鲀）的关系较远，而不是与植物的关系。有趣的是，在源自海洋的微生物中发现了ros同源物，支持了ros可能起源于海洋生物而非陆地生物的假说。
