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Effects of pH on the uncoupled, coupled and pre‐steady‐state currents at the amino acid transporter KAAT1 expressed in Xenopus oocytes
Author(s) -
Peres Antonio,
Bossi Elena
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.t01-1-00083.x
Subject(s) - xenopus , heterologous expression , transporter , chemistry , cotransporter , biophysics , voltage clamp , amino acid , reversal potential , steady state (chemistry) , ion transporter , biochemistry , patch clamp , membrane potential , recombinant dna , biology , sodium , membrane , gene , receptor , organic chemistry
1 The effects of pH on the different kinds of currents occurring at the lepidopteran amino acid cotransporter KAAT1 have been examined using heterologous expression in Xenopus oocytes and voltage clamp. 2 Acidic pH (5.5‐4.5) caused a slight depression of the uncoupled current and a complete inhibition of the coupled and transient currents, in the presence of either Na + or K + , the two ions physiologically relevant to the transport process. 3 Conversely, at alkaline pH (9) no statistically significant effects could be observed on uncoupled, coupled and transient currents compared to the effects at pH 7.6. 4 These effects of pH indicate that operation of the transporter is maximal in the physiologically alkaline native environment. 5 The dose‐response curves for the inhibition of coupled and transient currents were similar, with respective p K a values of 6.29 ± 0.05 and 6.40 ± 0.03 and respective Hill coefficient values ( n H ) of 0.93 ± 0.07 and 1.08 ± 0.08, suggesting that the two effects can be explained by a single proton binding to the same site in the transporter.