FIGURE 2.

Proline sites examined in this study. A, GLIC subunit structure, indicating proline residues (PDB: 3EHZ). B, conventional mutagenesis of GLIC Pro residues. Substitution with Ala mostly had little or no effect on pH₅₀ values, although P119A and P203A were nonfunctional, and P198A had increased sensitivity. P6-9A indicates simultaneous substitution of prolines at sites 6, 7, 8, and 9 with Ala; individual Ala substitutions at these sites yielded similar pH₅₀ values (not shown). Data shown are mean ± S.E., n = 3–4. *, pH-induced responses were comparable with uninjected cells. Typical maximal responses for WT and all Ala-containing mutants were 20–40 μA, except for P14A, where maximal responses were 2–5 μA.