Table 2.
High conservation of residues facing the channel interior in all FNT channelsa
| Residueb | Residues in the positionc | Conservation (%)d | Remarkse |
|---|---|---|---|
| I45 (TM1) | I(55), V, M, L | 96.7 | Hydrophobic |
| F75 (TM2a) | F(79), Y | 98.8 | Part of the central constriction |
| C82 (TM2a) | V(52), I, L | 93.0 | Hydrophobic |
| V83 (TM2a) | V(39), I(33), L, M | 86.7 | Hydrophobic |
| D88 (Ω-loop) | E(58), D | 80.7 | Acidic |
| L89 (Ω-loop) | L(99) | 99.9 | Part of cytoplasmic slit (closed) |
| T91 (Ω-loop) | T(98) | 97.9 | Part of cytoplasmic slit (closed) |
| S92 (Ω-loop) | G(50), S, A | 79.1 | End of Ω-loop; small and weakly polar |
| N121 (TM3) | N(99) | 99.4 | Hydrophilic, invariant |
| A171 (TM4) | C(62), S, A, G | 99.9 | Close to S-loop; small and weakly polar |
| N172 (TM4) | N(78) | 78.4 | Part of cytoplasmic slit (open) |
| V175 (TM4) | V(81), I, M | 99.9 | Part of cytoplasmic slit (closed) |
| V179 (TM4) | V(64), I, L, M | 86.2 | Hydrophobic |
| K191 (TM5a) | K(83), R, E | 96.4 | Basic |
| M195 (TM5a) | I(43), M, V, L | 88.2 | Hydrophobic |
| V199 (TM5a) | I(39), L, V | 76.9 | Hydrophobic |
| F202 (TM5) | F(78) | 78.5 | Part of central constriction ring |
| G206 (S-loop) | G(74), S, T | 79.0 | Small and weakly polar |
| H209 (S-loop) | H(99) | 98.7 | Part of central constriction ring |
| N213 (TM5b) | N(76) | 76.5 | Hydrophilic |
| N262 (TM6) | N(100) | 100.0 | Hydrophilic, invariant |
aAll 2206 FNT channels from bacteria, archaea and eukaryotes were considered for this analysis
bResidue numbers correspond to that of formate channel structure as available in the PDB ID: 3KCU. Occurrence of these residues in the transmembrane segsments or the functionally important loop regions is also indicated. Residues forming the two constriction regions are shown in bold and italic
cPercentage conservation of the most frequently observed residue(s) is indicated in brackets
dPercentage conservation as observed in all 2206 FNT channels
eChemical nature or the location with respect to the channel interior of the conserved residue is mentioned