CACNA1C and familial long QT syndrome: Interestingly, when CaM is preassociated with Cav1.2-IQ1665-1685, we demonstrated that the Kd for Cav1.2-NSCaTE51-67 is still significantly increased for the LQTS-associated variant, from 2.23 μM (CaM-WT) to 25.2 μM (CaM-E140G).