Effects of substrate concentration on the quaternary structure of the R298A mutant. (A) Continuous (c(s)) distribution of the R298A mutant at TQ6-pNA concentrations of 0 (solid circles), 20 (open circles), 120 (solid triangles), 250 (open triangles), 400 (solid squares), and 600 μM (open squares). (B) Sedimentation coefficient shift of R298A major species at different TQ6-pNA concentrations.