title: Transcription of the octopine catabolism operon of the Agrobacterium tumor-inducing plasmid pTiA6 is activated by a LysR-type regulatory protein.
abstract: 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.
authors.affiliation: Section of Microbiology, Cornell University, Ithaca, NY 14853.
authors.forename: L F
authors.initials: LF
authors.lastname: Habeeb
authors.forename: L
authors.initials: L
authors.lastname: Wang
authors.forename: S C
authors.initials: SC
authors.lastname: Winans
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics*; D000595:Amino Acid Sequence; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics*; D002874:Chromosome Mapping; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D009876:Operon; D010957:Plasmids; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C036483:T-DNA; D014157:Transcription Factors; C073469:OccR protein, Bacteria; C005394:octopine; C073470:LysR protein, Bacteria; D001120:Arginine