Figure 5.

A plot of A₂₆₀ for the free RNA peak, which is obtained by integrating the area under the peak in the s range of 2 to 2.6 S, against the molar ratio of PyrR to RNA in the sample. The data were obtained from the analytical ultracentrifugation experiment described in Fig. 4. The free RNA values were corrected for a slight loss of total A₂₆₀ ranging from 5% to 20%, of which a maximum of 5% was due to dilution. The dotted line shows a least -squares fit through the first 3 points. The horizontal dotted line shows the concentration of non-binding RNA from Fig. 4, Panel D in which the RNA peak is clearly defined. The intersection between the dashed and dotted lines indicates that 2 subunits of PyrR bind to 1 RNA stem-loop.