FIGURE 12.

Correlations between Cs⁺ block, Rb⁺ and spermine permeation, inward rectification, and agonist activation. (A–D) Correlation between inward rectification (g_{+40 mV}/g_{−100 mV}) and spermine current (at −130 mV; A), Rb⁺ current (at −130 mV; B), K_D (at −130 mV) of Cs⁺ block (C) and agonist activation (D). Agonist activation was calculated as the fractional increase of current (at −130 mV) on application of agonist (agonist activation was 0 if there was no increase and 1 if current doubled on application of agonist). (E–G) Correlation between agonist activation and spermine current (at −130 mV; E), Rb⁺ current (at −130 mV; F), and K_D (at −130 mV) of Cs⁺ block (G). Data were fitted with a Pearson correlation (P and R² values shown). Wild-type and mutant channels 1–21 were investigated in this study and mutant channels 22–35 were investigated in previous studies (9,16): 1 Kir3.1/Kir3.4 (wild-type); 2 Kir3.1-S-166L/Kir3.4; 3 Kir3.1/Kir3.4-A-172L; 4 Kir3.1-S-166L/Kir3.4-A-172L; 5 Kir3.1-S-166L-A-142T/Kir3.4; 6 Kir3.1-A-142T/Kir3.4; 7 Kir3.1-A-142V/Kir3.4; 8 Kir3.1/Kir3.4-T-148A; 9 Kir3.1/Kir3.4-T-148V; 10 Kir3.1-A-142T/Kir3.4-T-148A; 11 Kir3.1-A-142V/Kir3.4T-148-A; 12 Kir3.1-A-142V/Kir3.4-T-148V; 13 Kir3.1/Kir3.4-T-148A-A-172L; 14 Kir3.1-A-142T-S-166L/Kir3.4; 15 Kir3.1-A-142T-S-166L/Kir3.4-A-172L; 16 Kir3.1-S-166L/Kir3.4-T-148A-A-172L; 17 Kir3.1/Kir3.4-T-148A-E-145Q; 18 Kir3.1-A-142T-E-139Q/Kir3.4; 19 Kir3.1-A-142T/Kir3.4-T-148A-E-145Q; 20 Kir3.1-E-139Q/Kir3.4-T-148A; 21 Kir3.1-E-139Q/Kir3.4; 22 Kir3.1/Kir3.4-E-145Q; 23 Kir3.1-E-141Q/Kir3.4; 24 Kir3.1/Kir3.4-E-147Q; 25 Kir3.1/Kir3.4-R-155E; 26 Kir3.1-R-149E/Kir3.4-E-145Q; 27 Kir3.1/Kir3.4-E-145Q-R-155E; 28 Kir3.1-F-181M/Kir3.4; 29 Kir3.1/Kir3.4-F-187M; 30 Kir3.1-F-181A/Kir3.4-F-187A; 31. Kir3.1-F-181M/Kir3.4-F-187M; 32 Kir3.1-S-170P/Kir3.4-S-176P; 33 Kir3.1-D-173Q/Kir3.4; 34 Kir3.1/Kir3.4-E-231Q; and 35 Kir3.1-D-173Q/Kir3.4-E-231Q. Data corrected for junction potentials.