Constitutive mutations of Agrobacterium tumefaciens transcriptional activator virG

Department of Biochemistry, University of Minnesota, St. Paul 55108.
Journal of Bacteriology (Impact Factor: 2.81). 07/1992; 174(12):4169-74.
Source: PubMed

ABSTRACT The virulence (vir) genes of Agrobacterium tumefaciens Ti plasmids are positively regulated by virG in conjunction with virA and plant-derived inducing molecules. A procedure that utilizes both genetic selection and a genetic screen was developed to isolate mutations in virG that led to elevated levels of vir gene expression in the absence of virA and plant phenolic inducers. Mutants were isolated at a frequency of 1 in 10(7) to 10(8). Substitution mutations at two positions in the virG coding region were found to result in the desired phenotype. One mutant had an asparagine-to-aspartic acid substitution at residue 54, and the other contained an isoleucine-to-leucine substitution at residue 106. In both cases, the mutant phenotype required the presence of the active-site aspartic acid residue at position 52. Further analysis showed that no other substitution at residue 54 resulted in a constitutive phenotype. In contrast, several substitutions at residue 106 led to a constitutive phenotype. The possible roles of the residues at positions 54 and 106 in VirG function are discussed.

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Available from: Gregory J Pazour, Sep 26, 2015
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    • "RRs (Bourret et al., 1990; Pazour et al., 1992; Stewart et al., 1990). We hypothesize that, due to the complex domain structure of SypE, these mutations likely fail to mimic the conformational changes induced and/or stabilized by phosphorylation. "
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    Molecular Microbiology 08/2011; 82(1):114-30. DOI:10.1111/j.1365-2958.2011.07800.x · 4.42 Impact Factor
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    • "Strain EHA105 (Hood et al., 1993) containing the binary vector pAD1624 (Fig. 1b) (Abuodeh et al., 2000), constructed by A. Das and called EHA105/pAD1624, was also used. pAD1624 contains a constitutive virG gene (virGN54D) which facilitates transformation without the need to add acetosyringone for induction of the vir genes (Pazour et al., 1992). In both binary vectors the Hyg R gene from pCB1004 (Carroll et al., 1994) is present between the T- DNA borders (Fig. 1b). "
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    Fungal Genetics and Biology 11/2007; 44(10):1035-49. DOI:10.1016/j.fgb.2007.05.001 · 2.59 Impact Factor
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    • "VirG and the VirG homologues from several A. tumefaciens plasmids share over 72% identity over their entire lengths. The M. loti VirG protein contains the asparagine residue at position 54 that, when mutated to an aspartic acid residue, results in VirG variants that constitutively activate vir gene expression (Han et al. 1992; Jin et al. 1993; Pazour et al. 1992; Scheeren-Groot et al. 1994). Therefore, an analogous M. loti virGN54D mutant was constructed by site-directed mutagenesis as described in Materials and Methods, and the gene and its promoter region were cloned into the broad-host-range vector pFAJ1700 to produce pAH4. "
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