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TABLE I

Rate Data for HCN2 Channels and Fractional Activation Data for CNGA1 Channels


HCN2 channel

RatecAMP/RateControl

CNGA1 channel

Imax cAMP/Imax cGMP
Wild type (7) 3.6 ± 0.48 CNGA1cys-free (14) 0.055 ± 0.01 
K472E (4) 0.98 ± 0.04 R431E (5) 0.95 ± 0.01 
E502K (6) 2.2 ± 0.37 E462R (5) 0.38 ± 0.05 
K472E + E502K (4) 2.3 ± 0.52 R431E + E462R (3) 0.82 ± 0.04 
  R431D (5) 0.92 ± 0.03 
D542K (5) 2.7 ± 0.99 D502R (3) 0.18 ± 0.03 
K472E + D542K (3) 2.3 ± 1.0 R431D + D502R (3) 0.11 ± 0.03 
E502K + D542K (5)
 
1.0 ± 0.05
 

 

 

HCN2 channel

RatecAMP/RateControl

CNGA1 channel

Imax cAMP/Imax cGMP
Wild type (7) 3.6 ± 0.48 CNGA1cys-free (14) 0.055 ± 0.01 
K472E (4) 0.98 ± 0.04 R431E (5) 0.95 ± 0.01 
E502K (6) 2.2 ± 0.37 E462R (5) 0.38 ± 0.05 
K472E + E502K (4) 2.3 ± 0.52 R431E + E462R (3) 0.82 ± 0.04 
  R431D (5) 0.92 ± 0.03 
D542K (5) 2.7 ± 0.99 D502R (3) 0.18 ± 0.03 
K472E + D542K (3) 2.3 ± 1.0 R431D + D502R (3) 0.11 ± 0.03 
E502K + D542K (5)
 
1.0 ± 0.05
 

 

 

All values are mean ± SEM. The n values are in parentheses after each channel construct. HCN2 channel rates (1/τ): time constants (τ) were calculated from single-exponential fits to currents in response to voltage pulses to −130 mV, either in the presence or absence of cAMP.

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