Interaction of the virulence protein VirF of Agrobacterium tumefaciens with plant homologs of the yeast Skp1 protein.
The infection of plants by Agrobacterium tumefaciens leads to the formation of crown gall tumors due to the transfer of a nucleoprotein complex into plant cells that is mediated by the virulence (vir) region-encoded transport system (reviewed in [1-5]). In addition, A. tumefaciens secretes the Vir proteins, VirE2 and VirF, directly into plant cells via the same VirB/VirD4 transport system [6], and both assist there in the transformation of normal cells into tumor cells. The function of the 22 kDa VirF protein is not clear. Deletion of the virF gene in A. tumefaciens leads to diminished virulence [7, 8] and can be complemented by the expression of the virF gene in the host plant. This finding indicates that VirF functions within the plant cell [8]. Here, we report that the VirF protein is the first prokaryotic protein with an F box by which it can interact with plant homologs of the yeast Skp1 protein. The presence of the F box turned out to be essential for the biological function of VirF. F box proteins and Skp1p are both subunits of a class of E3 ubiquitin ligases referred to as SCF complexes. Thus, VirF may be involved in the targeted proteolysis of specific host proteins in early stages of the transformation process.
Institute of Molecular Plant Sciences, Clusius Laboratory, Leiden University, AL Leiden, The Netherlands.
B
B
Schrammeijer
E
E
Risseeuw
W
W
Pansegrau
T J
TJ
Regensburg-Tuïnk
W L
WL
Crosby
P J
PJ
Hooykaas
D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000472:pathogenicity; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D001483:Base Sequence; D001665:Binding Sites; D018797:Cell Cycle Proteins; D018744:DNA, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins; D044843:SKP Cullin F-Box Protein Ligases; D012441:Saccharomyces cerevisiae; D017386:Sequence Homology, Amino Acid; D014774:Virulence; D037521:Virulence Factors
C120363:ASK1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; D018744:DNA, Plant; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D044786:S-Phase Kinase-Associated Proteins; D037521:Virulence Factors; C484058:ASK2 protein, Arabidopsis; D044843:SKP Cullin F-Box Protein Ligases; C427884:ASK10 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases