FIG. 7.

Sedimentation equilibrium analysis of the dimerization of VirB8. Analytical ultracentrifugation to analyze the self-association of wild-type VirB8 alone (WT) or in the presence of B8I-2 (WT + B8I-2) and of the dimer site variant VirB8^M102R (M102R). The lower graphs show a representative fit of the experimental data to a monomer/dimer model in the case of VirB8 and to a single-species (i.e., monomer) model in the case of VirB8 plus B8I-2 and M102R. The upper graphs show the residuals of the fit. The representative fits shown here were taken from the data obtained for proteins at an A₂₈₀ of 0.5 and rotor speeds of 20,000, 24,000, and 28,000 rpm in a Beckman Coulter XL-A analytical ultracentrifuge.