A channel recording showing the effect of 10 μM heme-L-lysinate (Heme) and 0.5–1 mM NADPH on the activity of the 70-S K⁺ channel in an inside-out patch. The channel-closed level is indicated by C, and the pipette holding potential was –20 mV. The top trace is the time course of experiments. Three parts of the trace, indicated by numbers 1–3, are extended at a fast time resolution. NADPH, nicotinamide adenine dinucleotide phosphate.