Table III. Amino acid substitutions at key residues of FaNaC TM1.
Residue | Substitution | pNa+/pK+ |
---|---|---|
Wild type | none | 2.84 ± 0.49 |
Val89 | arginine | inactive |
lysine | 2.14 ± 0.41 | |
tyrosine | 2.36 ± 0.54 | |
Thr79 | phenylalanine | 2.67 ± 0.24 |
aspartic acid | inactive | |
Leu72 | glycine | 2.48 ± 0.24 |
phenylalanine | 4.96 ± 0.46 | |
tyrosine | inactive | |
aspartic acid | inactive |
Various substitutions were introduced by site-directed mutagenesis, and the corresponding mutants were tested for their functional expression, and selectivity between sodium and potassium (pNa+/pK+). Note the presence of several inactive mutants for each tested position, and the change of relative permeability observed for the Leu72Phe mutant.