Figure 4.

The current–voltage relationships obtained from the triple mutant GlyR. A ring of five proline residues lining the selectivity filter is deleted. In addition, five glutamate residues are inserted in the position indicated in Fig. 1A Inset, and the arginine residues in the external vestibule are replaced by glutamate residues. (A) The NaCl current–voltage curves obtained with the radius of the selectivity filter fixed at 4.15 Å (filled circles) and 3.80 Å (filled diamonds) are superimposed on the experimental data (open circles). (B) The CaCl₂ current–voltage relationship still exhibits outwards rectification and currents approximately one-third the magnitude seen for NaCl.