ABSTRACT
Ros is a chromosomally-encoded repressor containing a novel C2H2 zinc finger in Agrobacterium tumefaciens. Ros regulates the expression of six virulence genes and an oncogene on the Ti plasmid. Constitutive expression of these genes occurs in the spontaneous mutant 4011R derived from the octopine strain Ach-5, resulting in T-DNA processing in the absence of induction, and in the biosynthesis of cytokinin. Interestingly, the mutation in 4011R is an Arg to Cys conversion at amino acid residue 125 near the C-terminus well outside the zinc finger of Ros. Yet, Ros bearing this mutation is unable to bind to the Ros-box and is unable to complement other ros mutants.
Subject(s)
Agrobacterium tumefaciens/pathogenicity , Amino Acid Substitution , Bacterial Proteins , DNA-Binding Proteins/genetics , Plasmids/genetics , Repressor Proteins/genetics , Zinc Fingers/genetics , Agrobacterium tumefaciens/genetics , Agrobacterium tumefaciens/growth & development , DNA, Bacterial/genetics , DNA-Binding Proteins/chemistry , Electrophoresis, Polyacrylamide Gel , Immunoblotting , Mutation , Repressor Proteins/chemistry , Virulence/geneticsABSTRACT
C2H2 zinc finger bearing proteins are a large superfamily of nucleic acid binding proteins, which constitute a major subset of eukaryotic transcription factors. Although originally thought to occur only in eukaryotes, a novel C2H2 zinc finger transcription factor, Ros, which regulates both prokaryotic and eukaryotic promoters has been found in bacteria. Phylogenically, Ros is distantly related to eukaryotic zinc finger regulators.
