Mutational analysis of the transcriptional activator VirG of Agrobacterium tumefaciens.
To find VirG proteins with altered properties, the virG gene was mutagenized. Random chemical mutagenesis of single-stranded DNA containing the Agrobacterium tumefaciens virG gene led with high frequency to the inactivation of the gene. Sequence analysis showed that 29% of the mutants contained a virG gene with one single-base-pair substitution somewhere in the open reading frame. Thirty-nine different mutations that rendered the VirG protein inactive were mapped. Besides these inactive mutants, two mutants in which the vir genes were active even in the absence of acetosyringone were found on indicator plates. A VirG protein with an N54D substitution turned out to be able to induce a virB-lacZ reporter gene to a high level even in the absence of the inducer acetosyringone. A VirG protein with an I77V substitution exhibited almost no induction in the absence of acetosyringone but showed a maximum induction level already at low concentrations of acetosyringone.
Scheeren-Groot
E P
EP
Institute of Molecular Plant Sciences, Clusius Laboratory, Leiden University, The Netherlands.
Rodenburg
K W
KW
den Dulk-Ras
A
A
Turk
S C
SC
Hooykaas
P J
PJ
D000098:Acetophenones / Q000494:pharmacology; D016960:Agrobacterium tumefaciens / Q000235:genetics* / Q000472:pathogenicity; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004277:DNA, Single-Stranded / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009153:Mutagens; D016366:Open Reading Frames / Q000235:genetics; D010941:Plant Tumors / Q000382:microbiology; D010944:Plants / Q000382:microbiology; D017354:Point Mutation; D012641:Selection, Genetic; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic
D000098:Acetophenones; D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D009153:Mutagens; D014157:Transcription Factors; C058483:virG protein, Shigella flexneri; C051667:acetosyringone