Figure 1.
Similar extent of modulation of CNG channels by tyrosine phosphorylation and Ca2+/CaM. A, cGMP dose-response curves of rod CNG channels under conditions that promote phosphorylation or dephosphorylation. To maximize phosphorylation (circles), intact oocytes were preincubated with pervanadate for 30 min, and patches were continuously exposed to vanadate after excision. To maximize dephosphorylation (triangles), patches were exposed to vanadate-free solution for 5 min. Continuous curves show fits to the Hill equation. B, cGMP dose-response curves obtained before (triangles) and during (circles) application of Ca2+/CaM. For this experiment, CNG channels were first allowed to dephosphorylate for 5 min in vanadate-free saline before cGMP was applied.