Agrobacterium tumefaciens VirC2 enhances T-DNA transfer and virulence through its C-terminal ribbon-helix-helix DNA-binding fold.
Agrobacterium tumefaciens VirC2 stimulates processing of single-stranded T-DNA that is translocated into plants to induce tumor formation, but how VirC2 functions is unclear. Here, we report the 1.7-A X-ray crystal structure of its trypsin-resistant C-terminal domain, VirC2(82-202), which reveals a form of the ribbon-helix-helix (RHH) DNA-binding fold contained within a single polypeptide chain. DNA-binding assays and mutagenesis indicate that VirC2 uses this RHH fold to bind double-stranded DNA but not single-stranded DNA. Mutations that severely affect VirC2 DNA binding are highly deleterious for both T-DNA transfer into yeast and the virulence of A. tumefaciens in different plants including Nicotiana glauca and Kalanchoe daigremontiana. These data suggest that VirC2 enhances T-DNA transfer and virulence through DNA binding with its RHH fold. The RHH fold of VirC2 is the first crystal structure representing a group of predicted RHH proteins that facilitate endonucleolytic processing of DNA for horizontal gene transfer.
Lu
Jun
J
Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
den Dulk-Ras
Amke
A
Hooykaas
Paul J J
PJ
Glover
J N Mark
JN
D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology*; D001665:Binding Sites; D004269:DNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D014774:Virulence / Q000502:physiology*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C036483:T-DNA