Table 1.
Overview of studied mutants
| Mutant | Peak position, cm−1 | pKa | Sugar/H+ symport | Discussed role of studied residue |
| LacY WT | 1,747 | 10.5 | Yes | |
| LacYww | 1,747 | 10.5 | No | |
| E325A | No signal | nd | No sugar/H+ symport, but transmembrane sugar exchange (1, 2, 15) | H+ translocation |
| Mutants | LacYww | |||
| E325A | No signal | nd | No sugar/proton symport, but transmembrane sugar exchange (1, 2) | H+ translocation |
| E325D | 1,730 | 8.3 | 15% of WT (8, 16) | H+ translocation |
| R302K | 1,758/1,743 | 8.4 | No | H+ translocation |
| R302A | 1,741 | 10.3 | No sugar/H+ symport, but transmembrane sugar exchange (15, 16) | H+ translocation |
| H322Q | 1,734 | 10.1 | No | Ligand to sugar |
| Y236F | — | — | Decreased binding affinity and little transport | Hydrogen bond donor to H322 stabilizing its conformation |
| D240A | 1,749 | 9.8 | No | Salt-bridged K319/D240 |
| F243W | 1,740 | 10.1 | 30% of WT | |
| K319L | 1,750 | 10 | Reduced binding | Salt-bridged K319/D240 |
| L329F | — | — | No | Part of hydrophobic pocket around E325 |
nd, not determined.