Zn²⁺ slows activation in I287H+A359H+F290W+R1K+K5R channels. (A) Currents were evoked by depolarizing to +60 mV in the absence or presence of Zn²⁺: black, 0 µM; red, 1 µM; green, 10 µM. Traces have been scaled to the same amplitude and overlaid. Currents were fitted with one exponential component (black lines) to obtain values for τ_act. (B) The box plot shows values of τ_act measured at +60 mV in I287H+A359H+F290W+R1K+K5R or the F290W+R1K+K5R control channel as a function of Zn²⁺ concentration. Mean values of τ_act that differed significantly from no Zn²⁺ are indicated: #, P < 0.001; §, P < 0.0005 (n = 6–15).