The N-terminal domain of VirG of Agrobacterium tumefaciens: modelling and analysis of mutant phenotypes.

Fourteen mutants in the N-terminal domain of virulence factor G (VirG) were obtained by random mutagenesis. Two mutants showed an altered phenotype, all others were non-functional. All mutants can still be phosphorylated and bind to DNA. A 3-D model was built based on the coordinates of chemotaxis protein Y (CheY). Many of the observed phenotypic changes of VirG are explained qualitatively. Combination of model building and biochemical information leads to the conclusion that the active sites of VirG and CheY must partly use different residues to perform the same phosphorylation and dephosphorylation reactions.