FIGURE 7.
R179H actin binds less cooperatively to the transcription factor MRTF-A than WT SM α-actin. A, rate of polymerization of WT SM α-actin (blue) or R179H actin (green) in the absence (solid line) or presence (dashed line) of MRTF-A (3 μm for WT, 1 μm for R179H). Error bars are S.E. The dashed curves are fits to the Hill equation as described under “Experimental Procedures.” The fits yield a Kd of 1.8 μm for WT and 1.1 μm for R179H. Hill coefficients are 3 for WT and 1.5 for R179H. B, rate of polymerization of WT SM α-actin (blue, repeated from A) or a 50:50 mixture of WT and R179H actin (gray) in the presence (dashed line) of 3 μm MRTF-A. Error bars are S.E. The dashed curves are fits to the Hill equation as described under “Experimental Procedures.” The fits yield a Kd of 1.7 μm for the 50:50 mix of WT and R179H, and a Hill coefficient of 1.7.