Figure 3.

Gel-filtration chromatography of NtrC derivatives. Spin-labeled proteins at the concentrations indicated were sieved as described in Materials and Methods; the designation + P indicates that they were phosphorylated. Traces indicate absorbance at 280 nm, and the vertical bars indicate positions of elution of molecular mass standards used to calibrate the column (thyroglobulin, 669 kDa; ferritin, 440 kDa; catalase, 232 kDa; BSA, 67 kDa). Larger volumes were used for samples at 5 μM than at 25 μM (200 vs. 50 μl, respectively), and sensitivities of detection were set differently in the two cases.