The essential virulence protein VirB8 localizes to the inner membrane of Agrobacterium tumefaciens.

AUTOR(ES)

Thorstenson, Y R

RESUMO

Agrobacterium tumefaciens genetically transforms plant cells by transferring a specific DNA fragment from the bacterium through several biological membranes to the plant nucleus where the DNA is integrated. This complex DNA transport process likely involves membrane-localized proteins in both the plant and the bacterium. The 11 hydrophobic or membrane-localized proteins of the virB operon are excellent candidates to have a role in DNA export from agrobacteria. Here, we show by TnphoA mutagenesis and immunogold electron microscopy that one of the VirB proteins, VirB8, is located at the inner membrane. The observation that a virB8::TnphoA fusion restores export of alkaline phosphatase to the periplasm suggests that VirB8 spans the inner membrane. Immunogold labeling of VirB8 was detected on the inner membrane of vir-induced A. tumefaciens by transmission electron microscopy. Compared with that of the controls, VirB8 labeling was significantly greater on the inner membrane than on the other cell compartments. These results confirm the inner membrane localization of VirB8 and strengthen the hypothesis that VirB proteins help form a transfer DNA export channel or gate.

Documentos Relacionados

• Construction and characterization of Tn5virB, a transposon that generates nonpolar mutations, and its use to define virB8 as an essential virulence gene in Agrobacterium tumefaciens.
• Identification of a virB10 protein aggregate in the inner membrane of Agrobacterium tumefaciens.
• Functional Analysis of the Agrobacterium tumefaciens T-DNA Transport Pore Protein VirB8
• Genetic complementation analysis of the Agrobacterium tumefaciens virB operon: virB2 through virB11 are essential virulence genes.
• The lipoprotein VirB7 interacts with VirB9 in the membranes of Agrobacterium tumefaciens.