FIG. 3.

Effects of virB11 dominant mutations on T-pilus production. Exocellular fractions from PC1011 (designated ΔB11 or Δ) and A348 (designated A348 or A) strains expressing wild-type virB11 and alleles 1 to 12 were analyzed for accumulation of T-pilus-associated proteins, VirB2, VirB5, and VirB7, as listed on the left of each immunoblot. Strain Δ(B11) is pC1011(pSRB1) expressing PvirB::virB11, and strain Δ(PlacZ::B11) is PC1011(pPCB117) expressing PlacZ::virB11; alleles 1 to 12 expressed from PvirB are carried on plasmids pXZB101 to pXZB112. Plasmid pXZB104 was shown previously to encode a wild-type virB11 gene (69); however, we identified a mutation in the PvirB promoter of pXZ104 that results in a reduction in VirB11 production levels. M, molecular mass markers, with sizes in kilodaltons indicated on the right.