TABLE 3.
Consistency of models with experimental results
| Experiment (in Shaker unless indicated otherwise) | Our current | Transporter | Paddle |
|---|---|---|---|
| Biotin/avidin accessibility in KvAP (Jiang et al., 2003b) | yes | no | yes |
| S1 C-terminus, S2 N-terminus, and S1-S2 loop accessible from the outside in all conformations. (Gandhi et al., 2003) | yes | yes | no* |
| S3b and S3-S4 linker is accessible from outside in all conformations (Gandhi et al., 2003) | yes | yes | no |
| Hanatoxin binds to S3b of both open and resting conformations (Lee et al., 2003; Li-Smerin and Swartz, 2000, 2001) | yes | yes | no* |
| The Δ330–357 mutant gates normally, but residues on S3b and S4 are accessible to MTSET only at positive voltages (Gonzalez et al., 2004) | yes | ? | yes |
| N-terminus of S4 interacts with C-terminus of S5 at positive voltages (Elinder et al., 2001a,b; Laine et al., 2003; Gandhi et al., 2003; Broomand et al., 2003) | yes | yes | no* |
| S357C/E318C residues are proximal at negative voltages (Neale et al., 2003) | yes | yes | no |
| Cys mutants of S3-S4 loop residues 353–356 form disulfide bridges with S5 residue F416C at all voltages (Gandhi et al., 2003; Broomand et al., 2003) | yes | yes | no |
| Disulfide bridge cross-links S4 segments of different subunits (Aziz et al., 2002) | no | no | ? |
| R362H (R1) and R371H (R4) mutants form proton pores at negative and positive voltages (Starace et al., 1997; Starace and Bezanilla, 2004) | yes | yes | no |
| R365H (R2) & R368H (R3) mutants transport protons during activation/deactivation (Starace et al., 1997; 2004) | yes | yes | no |
| Voltage-dependent accessibility of S4 cysteine mutants to MTS reagents (Baker et al., 1998; Larsson et al., 1996; Yang et al., 1996; Gandhi et al., 2003) | yes | ? | no |
| Charges of adducts contribute to the gating current for R362C (R1) and R365C (R2) mutants but do not when adducts are at positions 363, 364, or 366 (Ahern and Horn, 2004) | yes | ? | no |
| R362 (R1) and R365 (R2) interact with E283 (E2a) in activated and transition conformations (Tiwari-Woodruff et al., 2000) | yes | ? | ? |
| K374 (K5) and R377 (R6) interact with E293 (E2b) and D316 (D3a) (Papazian et al., 1995) | yes | ? | ? |
| Distances of residues from the axis of the pore determined by LRET (Cha et al., 1999) | Almost all | yes | no |
| Tethered TEA analogs (Blaustein et al., 2000) | yes | ? | ? |
| Tolerance of S1–S3 residues to mutations (Li-Smerin et al., 2000b; Hong and Miller, 2000; Monks et al., 1999) | yes | ? | no* |
| Tolerance of residues on the outer surface of the pore-forming domain to mutations (Li-Smerin et al., 2000a) | yes | ? | ? |
Our current is the model presented in this article; Transporter is the model of Starace and Bezanilla (2004), in which the position of barriers that control access to crevasses changes during activation but S4 does not move much; and the Paddle model is that of Jiang et al. (2003a,b). An asterisk indicates that the assessment is only for the more explicit depiction of the paddle model in Fig. 5 of Jiang et al. (2003b). The question marks indicate uncertainty of the assessment.