Habeeb L F, Wang L, Winans S C
Section of Microbiology, Cornell University, Ithaca, NY 14853.
Mol Plant Microbe Interact. 1991 Jul-Aug;4(4):379-85. doi: 10.1094/mpmi-4-379.
Agrobacterium tumefaciens incites crown gall tumors on plant hosts by conjugally transferring a discrete fragment of oncogenic DNA. In addition to oncogenes, the transferred DNA contains genes that direct the synthesis and exudation of opines, which are used as nutrients by the bacteria. The bacterium contains one or more operons of Ti plasmid-encoded genes that are required for the internalization and utilization of opines, and transcription of these catabolic genes is induced by cognate opines. Here we localize the gene required for regulated expression of the octopine degradative operon of the pTiA6 plasmid to a 2-kb fragment of Ti plasmid DNA. The protein encoded by this DNA positively regulates the transcription of the catabolic operon in the presence of octopine. In addition, it negatively regulates its own gene in the presence or absence of octopine. The sequence of this gene was determined and analysis of the inferred protein sequence indicates that the gene encodes a member of the LysR family of prokaryotic transcriptional regulatory proteins.
根癌土壤杆菌通过接合转移致癌DNA的一个离散片段，在植物宿主上引发冠瘿瘤。除致癌基因外，转移的DNA还包含指导冠瘿碱合成和分泌的基因，冠瘿碱被细菌用作营养物质。该细菌含有一个或多个Ti质粒编码基因的操纵子，这些操纵子是冠瘿碱内化和利用所必需的，这些分解代谢基因的转录由同源冠瘿碱诱导。在这里，我们将pTiA6质粒章鱼碱降解操纵子的调控表达所需基因定位到Ti质粒DNA的一个2 kb片段上。该DNA编码的蛋白质在章鱼碱存在的情况下正向调节分解代谢操纵子的转录。此外，在有无章鱼碱的情况下，它都对自身基因进行负调节。测定了该基因的序列，对推导的蛋白质序列进行分析表明，该基因编码原核转录调节蛋白LysR家族的一个成员。
