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Biochemistry, Biophysics, and Structural Biology
K-pump • Na1–Na1 exchange current • HeLa cells • voltage clamp
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Electrogenic Sodium–Sodium Exchange Carried Out By Na,K-Atpase Containing The Amino Acid Substitution Glu779ala, José Argüello, R.Daniel Peluffo, Jerry Lingrel, Joshua Berlin
Electrogenic Sodium–Sodium Exchange Carried Out By Na,K-Atpase Containing The Amino Acid Substitution Glu779ala, José Argüello, R.Daniel Peluffo, Jerry Lingrel, Joshua Berlin
José M. Argüello
Na,K-ATPase containing the amino acid substitution glutamate to alanine at position 779 of the a subunit (Glu779Ala) supports a high level of Na-ATPase and electrogenic Na1–Na1 exchange activityin the absence of K1. In microsomal preparations of Glu779Ala enzyme, the Na1 concentration for half maximal activation of Na-ATPase activity was 161 6 14 mM (n 5 3). Furthermore, enzyme activity with 800 mM Na1 was found to be similar in the presence and absence of 20 mM K1. These results showed that Na1, with low affinity, could stimulate enzyme turnover as effectively as K1. To gain further insight into the mechanism …