Figure 4.

UBE2K-Ub₂ is monomeric in solution. The lower panels show triplicate sedimentation equilibrium data sets (A–C) for 10.9 μM UBE2K-Ub₂ collected using rotor speeds of 15,000 (solid black circles), 18,000 (solid red circles), and 21,000 (solid blue circles) rotations per minute at 5°C. Fitting of these data yielded a mass of 42,674 ± 564. The upper panel shows the residual errors between the best fit curve and data for each data set. All other details are described in the Materials and Methods.