1. Figure S1: Reaction mechanisms of NRs lacking CTDs alter channel kinetics. Kinetic models optimized by fitting 5C2O open state models to entire records obtained from 2A and 2B receptors. (p > 0.05). Rate constants (s -1 ) are given as rounded averages of means for each condition. * indicates values that are significantly different (lower in red and higher in blue) than the respective wild-type channels (p < 0.05).

2. Table S1: Kinetic analyses of open intervals. Time constants (  ) and areas (a) of individual open components estimated by fitting entire files to a kinetic model containing 5C4) states. Values in blue are significantly higher than WT (*, p < 0.05) Condition τ Ef (ms) a Ef (%) τ EL (ms) a EL (%) τ EM (ms) a EM (%) τ EH (ms) a EH (%) N1/2A0.14 ± 0.018.8 ± 0.92.6 ± 0.224 ± 55.9 ± 0.548 ± 411.1 ± 0.918 ± 3 N1 Δ /2A0.13 ± 0.016 ± 13.2 ± 0.332 ± 75.6 ± 0.550 ± 613 ± 112 ± 5 N1/2A Δ 0.13 ± 0.017 ± 14.2 ± 0.4*19 ± 414.0 ± 0.8*57 ± 433 ± 4*17 ± 8 N1 Δ /2A Δ 0.17 ± 0.0310 ± 13.1 ± 0.429 ± 710.2 ± 0.8*39 ± 427 ± 5*22 ± 10 N1/2B0.19 ± 0.037 ± 22.6 ± 0.430 ± 96.4 ± 0.442 ± 411.4 ± 0.621 ± 8 N1 Δ /2B0.13 ± 0.019 ± 12.4 ± 0.221 ± 55.7 ± 0.452 ± 410 ± 117 ± 6 N1/2B Δ 0.16 ± 0.018 ± 11.9 ± 0.214 ± 28.0 ± 0.855 ± 318 ± 2*21 ± 6 N1 Δ /2B Δ 0.20 ± 0.029 ± 12.5 ± 0.423 ± 29.9 ± 0.6*42 ± 224 ± 1*25 ± 3

3. Condition τ E1 (ms) a E1 (%) τ E2 (ms) a E2 (%) τ E3 (ms) a E3 (%) τ E4 (ms) a E4 (%) τ E5 (ms) a E5 (%) N1/2A0.14 ± 0.0145 ± 31.4 ± 0.124 ± 24.4 ± 0.230 ± 322 ± 41.5 ± 0.33,000 ± 4000.08 ± 0.01 N1 Δ /2A0.14 ± 0.0150 ± 31.5 ± 0.137 ± 3*5.1 ± 0.512 ± 1*47 ± 6*1.6 ± 0.52,900 ± 3000.08 ± 0.02 N1/2A Δ 0.15 ± 0.0246 ± 42.0 ± 0.346 ± 4*7 ± 111 ± 2*900 ± 400*0.5 ± 0.1*8,000 ± 1,000*0.7 ± 0.1* N1 Δ /2A Δ 0.22 ± 0.03*39 ± 32.9 ± 0.5*41 ± 2*12 ± 1*17 ± 2*600 ± 200*1.1 ± 0.38,600 ± 800*1.3 ± 0.1* N1/2B0.17 ± 0.0136 ± 52.7 ± 0.918 ± 512 ± 341 ± 334 ± 46 ± 21,130 ± 800.4 ± 0.2 N1 Δ /2B0.15 ± 0.0135 ± 32.0 ± 0.217 ± 29.2 ± 0.738 ± 739 ± 66 ± 11,380 ± 40*0.5 ± 0.1 N1/2B Δ 0.14 ± 0.01*33 ± 32.9 ± 0.422 ± 318 ± 235 ± 3230 ± 80*7 ± 12,300 ± 500*2.9 ± 0.5* N1 Δ /2B Δ 0.14 ± 0.01*38 ± 32.7 ± 0.324 ± 319 ± 330 ± 5300 ± 100*6 ± 13,100 ± 500*2.2 ± 0.5* Table S2: Kinetic analyses of closed intervals Time constants (  ) and areas (a) of individual closed components (E1-E5) estimated by fitting entire files to a kinetic model containing 5C4O states. *, values that are significantly different relative to WT (p < 0.05), highlighted in red (lower) or blue (higher)