Phe(475) and Glu(446) but not Ser(445) participate in ATP-binding to the alpha-subunit of Na(+)/K(+)-ATPase.
The ATP-binding site of Na(+)/K(+)-ATPase is localized on the large cytoplasmic loop of the alpha-subunit between transmembrane helices H(4) and H(5). Site-directed mutagenesis was performed to identify residues involved in ATP binding. On the basis of our recently developed model of this loop, Ser(445), Glu(446), and Phe(475) were proposed to be close to the binding pocket. Replacement of Phe(475) with Trp and Glu(446) with Gln profoundly reduced the binding of ATP, whereas the substitution of Ser(445) with Ala did not affect ATP binding. Fluorescence measurements of the fluorescent analog TNP-ATP, however, indicated that Ser(445) is close to the binding site, although it does not participate in binding.
Kubala
Martin
M
Institute of Physiology, Academy of Sciences of the Czech Republic, Vi;denská 1083, CZ-142 20, Prague 4, Czech Republic.
Hofbauerová
Katerina
K
Ettrich
Rüdiger
R
Kopecký
Vladimír
V
Krumscheid
Rita
R
Plásek
Jaromír
J
Teisinger
Jan
J
Schoner
Wilhelm
W
Amler
Evzen
E
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D005456:Fluorescent Dyes / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D010649:Phenylalanine / Q000378:metabolism; D011487:Protein Conformation; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D005456:Fluorescent Dyes; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D018698:Glutamic Acid; D012694:Serine; D010649:Phenylalanine; C045674:2',3'-O-(2,4,6-trinitro-cyclohexadienylidine)adenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase