Extended Data Figure 5. Shark K_V gating currents.

a. Gating currents recorded in HEK293 cells expressing nonconductive shark (red) or human (black) K_V1.3 elicited by increasing voltage pulses in 10mV increments from a −100mV holding potential.

b. Average charge (Q)-V relationships. Shark K_V1.3 V_a1/2 was −33.4 ± 0.5mV, K_a = 6.1 ± 0.5mV and human K_V1.3 V_a1/2 was −54.25 ± 0.7mV, K_a = 5.2 ± 0.6mV. n = 9, p < 0.0001 for V_a1/2 two-tailed Student’s t-test. Dotted lines indicate associated G–V relationships.

c. Q_ON kinetics following voltage sensor activation from a holding potential of −100 mV were significantly slower in shark (red) compared with human (black). n = 7, p < 0.0001 for contribution of orthologue identity to series variance, two-way ANOVA with post hoc Bonferroni test.

d. Representative OFF gating current (Q_OFF) kinetics during repolarization in 10mV increments following a 40mV prepulse. Arrow indicates when deactivation rates were measured and purple traces show deactivation at −50 mV.

e. Q_OFF kinetics were significantly faster in shark (red) compared with human (black). n = 11, p < 0.0001 for contribution of orthologue identity to series variance, two-way ANOVA with post hoc Bonferroni test.

f. Gating currents recorded in HEK293 cells expressing nonconductive shark (red) or human (black) K_V1.3 following decreasing voltage pulses in increments of 10mV from a holding potential of 0 mV. Scale bars, 500 pA, 25 ms.

g. Average charge (Q)-V relationships of downward voltage sensor movement (Q_OFF) in response to decreasing voltage pulses from a holding potential of 0 mV. Shark K_V1.3 V_a1/2 was −61.6 ± 1.9 mV and human K_V1.3 V_a1/2 was −110.9 ± 1.01 mV. n = 7, p < 0.0001 for contribution of orthologue identity to series variance, two-way ANOVA with post hoc Bonferroni test.

h. Q_OFF kinetics of voltage sensor deactivation from a holding potential of 0 mV were significantly faster in shark (red) compared with human (black). n = 7, p < 0.0001 for contribution of orthologue identity to series variance, two-way ANOVA with post hoc Bonferroni test.

All data represented as mean ± s.e.m.

i. Ion tail currents (indicating channel closure) deactivated faster in shark (red) compared with human (black) K_V1.3. Tail currents were measured at −100mV following a series of activating voltage pulses that increased in 10mV increments. Inset: Arrows indicate when tail currents were measured following activating voltage pulses. Representative of n = 10. τ for deactivation from 60 mV pulse: shark = 1.5 ± 0.1ms, human = 5.5 ± 0.4ms. p < 0.0001, two-tailed Student’s t-test.