title: virG, an Agrobacterium tumefaciens transcriptional activator, initiates translation at a UUG codon and is a sequence-specific DNA-binding protein.
abstract: The Agrobacterium tumefaciens Ti plasmid virG locus, in conjunction with virA and acetosyringone, activates transcription of the virulence (vir) genes. Insertional and deoxyoligonucleotide-directed mutagenesis studies showed that both octopine and nopaline Ti plasmid virG genes initiate translation at a UUG codon. VirG protein initiated at this UUG codon was found to be 241 amino acid residues in length and had an apparent molecular mass of 27.1 kilodaltons. A Salmonella typhimurium trp-virG transcriptional fusion was constructed to overproduce VirG. Agrobacterium cells containing this gene fusion showed a large increase in virG activity in the presence of virA and acetosyringone. Since the trp promoter is not under virA-virG control, this result indicates that modification of VirG is necessary for its full activity. VirG overproduced in Escherichia coli was purified from inclusion bodies. It was found to be a DNA-binding protein that preferentially bound DNA fragments containing the 5' nontranscribed regions of the virA, -B, -C, -D, and -G operons. Significant specific binding to the 5' nontranscribed region sequences of virE was not detected. DNase I footprinting of the upstream regions of virC-virD and virG showed that VirG binds to sequences around the vir box region.
authors.affiliation: Department of Biochemistry, University of Minnesota, St. Paul 55108.
authors.forename: G J
authors.initials: GJ
authors.lastname: Pazour
authors.forename: A
authors.initials: A
authors.lastname: Das
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D003062:Codon / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D015345:Oligonucleotide Probes; D010957:Plasmids; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics*; D012231:Rhizobium / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D014157:Transcription Factors; D015533:Transcriptional Activation; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D003062:Codon; D004268:DNA-Binding Proteins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D014157:Transcription Factors; C058483:virG protein, Shigella flexneri