Figure 7.

CaM binding to CNGB1 linchpin mutants (CaM1^F575E, CaM2^L1132E, and CaM2^L1136E). ITC isotherms of the CaM N-lobe binding to CaM1^F575E (A) and CaM C-lobe binding to CaM2^L1132E (B) and CaM2^L1136E (C). Each isotherm was fit to a one-site model, and the binding parameters (ΔH and K_d) are given in Table 1. The experimental conditions are provided in the Materials and Methods section. NMR spectra of (D) CaM1^WT (black) and CaM1^F575E (red) and (E) CaM2^WT (black), CaM2^L1132E (red), and CaM2^L1136E (blue) suggest that CaM1 and CaM2 both form an α-helix and the mutants are structurally intact.