Pleiotropic phenotypes caused by genetic ablation of the receiver module of the Agrobacterium tumefaciens VirA protein

• Published in: Journal of Bacteriology 1996-08, Vol.178 (15), p.4710-4716
• Main Authors: Chang, C. (Cornell University, Ithaca, NY.), Zhu, J, Winans, S.C
• Format: Article
• Language: English
• Subjects: ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; AGROBACTERIUM TUMEFACIENS; Agrobacterium tumefaciens - drug effects; Agrobacterium tumefaciens - genetics; Agrobacterium tumefaciens - metabolism; Alleles; BACTERIA; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Base Sequence; BETA GALACTOSIDASA; BETA GALACTOSIDASE; COMPOSE PHENOLIQUE; COMPUESTOS FENOLICOS; DNA, Bacterial - genetics; EXPRESION GENICA; EXPRESSION DES GENES; FENOTIPOS; GENE; Gene Expression; GENES; Genes, Bacterial; GENETICA; Genetics; GENETIQUE; Lac Operon; Molecular Sequence Data; Mutagenesis, Site-Directed; MUTANT; MUTANTES; Phenols - pharmacology; PHENOTYPE; Plasmids - genetics; PROTEINA QUINASA; PROTEINAS; PROTEINE; PROTEINE KINASE; Proteins; Sequence Deletion; Virulence Factors
• ISSN: 0021-9193; 1098-5530; 1067-8832
• DOI: 10.1128/jb.178.15.4710-4716.1996

The VirA protein of Agrobacterium tumefaciens is a transmembrane sensory kinase that phosphorylates the VirG response regulator in response to chemical signals released from plant wound sites. VirA contains both a two-component kinase module and, at its carboxyl terminus, a receiver module. We previously provided evidence that this receiver module inhibited the activity of the kinase module and that inhibition might be neutralized by phosphorylation. In this report, we provide additional evidence for this model by showing that overexpressing the receiver module in trans can restore low-level basal activity to a VirA mutant protein lacking the receiver module. We also show that ablation of the receiver module restores activity to the inactive VirA (delta 324-413) mutant, which has a deletion within a region designated the linker module. This indicates that deletion of the linker module does not denature the kinase module, but rather locks the kinase into a phenotypically inactive conformation, and that this inactivity requires the receiver module. These data provide genetic evidence that the kinase and receiver modules of VirA attain their native conformations autonomously. The receiver module also restricts the variety of phenolic compounds that have stimulatory activity, since removal of this module causes otherwise nonstimulatory phenolic compounds such as 4-hydroxyacetophenone to stimulate vir gene expression