ATRA concentration is plotted versus the log of the KD for each RARα LBD to N-CoR or ACTR. A, ATRA binding affinity is largely unaffected by N-CoR binding. With the exception of M297L, affinity to ATRA does not differ significantly amongst the N-CoR-bound receptors, visualized by the similarly shaped ATRA-response curves. B, The presence of ACTR, however, has a large effect on ATRA binding affinity. The mutations, particularly L398P and I410T, weaken the ATRA affinity of ACTR-bound receptors, visualized by the diverse shapes of the ATRA-response curves.