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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 …
The Role Of Na,K-Atpase Alpha Subunit Serine 775 And Glutamate 779 In Determining The Extracellular K+ And Membrane Potential-Dependent Properties Of The Na,K-Pump, José Argüello, R.Daniel Peluffo, Joshua Berlin
The Role Of Na,K-Atpase Alpha Subunit Serine 775 And Glutamate 779 In Determining The Extracellular K+ And Membrane Potential-Dependent Properties Of The Na,K-Pump, José Argüello, R.Daniel Peluffo, Joshua Berlin
José M. Argüello
The roles of Ser775 and Glu779, two amino acids in the putative fifth transmembrane segment of the Na,K-ATPase a subunit, in determining the voltage and extracellular K1 (K1o) dependence of enzyme-mediated ion transport, were examined in this study. HeLa cells expressing the a1 subunit of sheep Na,K-ATPase were voltage clamped via patch electrodes containing solutions with 115 mM Na1 (378C). Na,K-pump current produced by the ouabain-resistant control enzyme (RD), containing amino acid substitutions Gln111Arg and Asn122Asp, displayed a membrane potential and K1o dependence similar to wild-type Na,K-ATPase during superfusion with 0 and 148 mM Na1-containing salt solutions. Additional substitution of …