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. 1999 Jan 19;96(2):754–759. doi: 10.1073/pnas.96.2.754

Figure 4.

Figure 4

(A) PsTx blocks CNG channels with nM affinities. Outside-out patches containing the α-subunit of the rat olfactory CNG channel (rOLF; •), the α-subunit of the bovine rod CNG channel (bRET; ○), or both the α- and β-subunits of the bovine rod CNG channel (bRETαβ; ⧫) were tested for their sensitivity to block by PsTx at −60 mV. Dose–response relations were fit by the Hill equation: I+PsTx/I−PsTx = Kin/([PsTx]n + Kin) to determine apparent affinities. The fit parameters for the curves shown were: rOLF −Ki = 5 nM, n = 1.2; bRET − Ki = 100 nM; n = 1.2; bRETαβ − Ki = 3.5 μM; n = 1.2. (B) Block by PsTx was slow to develop and reverse. Voltage pulses to +50 mV were given every 2.5 or 5 sec. to outside-out patches expressing the rat olfactory CNG channel α-subunit. Shown is the fractional current as a function of time after the application and removal of 125 nM PsTx (arrows). Thin lines show single exponential fits with rate constants kon = 4 × 105 M−1 sec−1 and koff = 2.1 × 10−3 sec−1.