Figure 6.

Proposed mechanism for suppression of Ca²⁺/CaM inhibition of rod CNG channels by phosphorylation of CNGA1_Y498. A, Ca²⁺/CaM inhibits rod CNG channels by binding to a Ca²⁺/CaM binding-site (CBS) on CNGB1 (B1) and disrupting its interaction with the C terminus of CNGA1 (A1) (Trudeau and Zagotta, 2002). B, Phosphorylation of CNGA1_Y498 also disrupts the interaction between the C terminus (C) of CNGA1 and the N terminus (N) of CNGB1. Thus, when Ca²⁺/CaM binds the CBS, there is no additional effect on the intersubunit interaction. C, Phosphorylation of CNGB1_Y1097 may disrupt a similar interface between the C-terminus region of CNGB1 and the N-terminus region of CNGA1. Binding of Ca²⁺/CaM to the Ca²⁺/CaM binding-site can still disrupt the interface between the C terminus of CNGA1 and the N terminus of CNGB1. Hence, phosphorylation of CNGB1_Y1097 has no effect on Ca²⁺/CaM inhibition. The cyclic-nucleotide binding domain is shown as a dotted line.