Table 5. Transport mechanism and energetics in RhBG proteins*.
| Mechanism* | Supporting evidence | Possible energetics | References |
|---|---|---|---|
| 7 |
Human RhBG - Ammonium pulse is associated with current in oocyte, not MeA pulse -14[C]-MeA uptake increases by outwardly pH gradient. - NH4+ transport induce pHi alkalinisation. |
Δψ dependent | [94] |
| 1 |
Mouse RhBG - ammonium pulse associated with current and induce a pHi acidification |
Δψ dependent | [95] |
| 1 or 8 |
Mouse RhBG -ammonium pulse associated with current and decrease pHi -MeA pulse associated with current and increase pHi |
Δψ dependent NH3 chemical gradient |
[96] |
| 8 |
Mouse RhBG -electrogenic transport is pH dependent -electroneutral transport is pH-independent |
Δψ dependent NH3 chemical gradient pH dependent |
[97] |
| 5 |
Human RhBG - Oocyte pHs fall after ammonium pulse on oocyte |
Potentially Δψ independent or NH4+ electrochemical gradient | [86] |
| 8 |
Mouse RhBG -Transport both NH4+/NH3 and MeA+/MeA but; -Electrogenic transport is favour for ammonium -Electroneutral transport is favour for MeA |
Δψ dependent NH3 chemical gradient pH dependent |
[87] |
| 5& |
Human RhBG - ammonium pulse associated with alkalanisation of cell expressing RhBC - pHi acidification when cell loaded with ammonium were pulse with ammornium-free buffer |
NH3 chemical gradient | [73] |
| 7 |
Mouse RhBG - Electroneutral transport of MeA in oocyte - Stimulated by outwardly pH gradient. |
pH gradient dependent Δψ independent |
[98] |
*
Mechanism: 1 - NH4+ uniport, 5 - NH3 uniport, 7 - NH4+/H+ antiport, 8 - Transport of both NH3 and NH4+, &- the activity may be bidirectional activity.