Mutations of I94 in the consensus sequences of P1.
A and B. Current voltage relations for the P1 mutant I94V in (A), 70mM [K+]o (●) and in 70mM [Rb+]o (○); and (B), 70mM [K+]o (●) and in 70mM [Na+]o (△); channels retain some selectivity in this mutant. C and D. Current voltage relations for I94S under similar experimental conditions (K+, ●; Rb+, ○; Na+, △); channels lose ionic selectivity with this less conservative mutation. E and F. Potential interactions of I94 and its equivalent in P2, I200 suggested by our modelling studies. The residues behind the selectivity filter, surrounding I94 (E); the residues behind the selectivity filter, surrounding I200 (F).