Calcium/CaM dependent inactivation (GDI) of L-type Ca2+channels (Cav1.2) has a vital role in excitation- contraction coupling. CaM binds via its C-domain to CaM-binding motifs on the C-terminal tail for GDI but the role of the N-domain of CaM is not known in this process. To dissect the role of the N-domain of CaM in the GDI of Cav1.2, the following specific aims are proposed: (1) Determine the affinity and calcium dependence of each domain of CaM binding to three CaM binding motifs in Cav1.2, (2) Determine how CaM binding to three CaM-binding motifs in Cav1.2 changes the "trigger point" of conformational change, and (3) Determine residues and sites of CaM important for binding to three CaM-binding motifs on Cav1.2. The first aim will identify the strength of association between CaM-binding motifs on the C-domain of Cav1.2 and CaM. The second aim will determine the effect of association with CaM-binding peptides on the free energy of calcium association of CaM domains. The third aim will identify residues on CaM that are important for binding to these CaM-binding motifs. These studies will lead to a better understanding of the role of CaM domains in regulating conformational change in Cav1.2 which plays an essential role in regulating heartbeat. [unreadable] [unreadable] [unreadable]