TABLE I.
Summary of Modulation of pH Sensitivity with Histidine Position in Loops A and C
| Aquaporin | Loop A | Loop C | Maximum pH sensitivity | Factor of increase |
|---|---|---|---|---|
| bAQP0 | His40 | His122 | pH 6.5 | 1.8 |
| bAQP0/H40C | — | His122 | pH 8.5 | 1.9 |
| bAQP0/H122Q | His40 | — | pH 6.5 | 1.5 |
| MIPfun | His39 | — | pH 8.5 | 2.2 |
| MIPfun/H39L/N40H | His40 | — | pH 6.5 | 1.8 |
| MIPfun/H43Q | His39 | — | pH 8.5 | 2.3 |
| MIPfun/Q122H | His39 | His122 | pH 8.5 | 1.5 |
| hAQP1 | — | — | none | none |
| hAQP1/D48H | His48 | — | pH 8.5 | 1.7 |
| hAQP1/D48H/A130H | His48 | His130 | pH 6.5 and pH 8.5 | 1.9 and 1.6 |
| rAQP4 | — | His129 | pH 8.5 | 1.9 |
The factor of increase is calculated by dividing the Pf at the maximum pH sensitivity by the Pf at pH 7.5.