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Figure 6.
Proton and potassium conductance of liposomes and
proteoliposomes. Shown is pH variation of liposomes (blue trace)
and proteoliposomes containing wild-type AmtB (black trace) or
the double variant F107A/F215A (red trace) when applying a pH
pulse of 1 unit by adding 5 mM KOH. The dashed line indicates
addition of 1 μM valinomycin in A and 1 μM FCCP (carbonyl
cyanide-p-trifluoromethoxyphenyl-hydrazone) in B. The arrow on
each trace indicates the addition of 1 μM FCCP in A and 1 μM
valinomycin in B. The alkalanization rate constant (k, s^−1)
resulting from the charge equilibration due to the equilibration
of H^+ (A) and K^+ movement (B) is noted above each trace. The
apparent proton permeabilities P′ [H], measured as described
in the text, were 2.0 × 10^−8, 2.8 × 10^−8, and
2.0 × 10^−8 cm/s for liposomes and proteoliposomes
containing wild-type AmtB or the double variant, respectively.
The apparent K^+ permeabilities P′ [K] were 1.5 ×
10^−8, 2.3 × 10^−8, and 2.5 × 10^−8 cm/s.
Experiments were performed at 20°C.
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