Spermine block of channels resulting from coexpression of a 1:1 molar ratio of S1-WT and S1-ND subunits reveals random coassembly. (A) Family of normalized, leak-subtracted ramp I/V curves, obtained in a patch from an oocyte injected with a 1:1 molar ratio of S1-WT+S1-ND cRNA; in the absence of (black line), or in the presence of 5 (red line), 20 (cyan line), 100 (blue line), and 1,000 μM (pink line) spermine. (B) Family of g_rel/V curves obtained from the I/V curves shown in A (solid symbols, color coding as in A). The family of solid black lines represents a 10-free parameter global fit to the ensemble of the four g_rel/V curves, assuming random coassembly. Obtained fit parameters were p = 0.46, K₀₁ = 7.02 μM, ρ₁ = 2.83, n_H1 = 0.97, K₀₂ = 247 μM, ρ₂ = 2.47, n_H2 = 0.77, K₀₃ = 2.30 mM, ρ₃ = 0.87, n_H3 = 0.77. The parameters for components 0 and 4 were fixed to the values shown in Table I. The family of dotted black lines represents the best global fit assuming no coassembly between S1-WT and S1-ND subunits. (C) Visual display of average fit parameters for components i = 0…4. Numbers in the top panel identify components.