3D Structure of Sodium/Potassium ATPase
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CPK Color Scheme C O N P |
Pressing this button will highlight the three subunits of the Na/K-ATPase. The alpha subunit, the main catalytic subunit, appears in wheat; the beta subunit appears in cyan; and the gamma subunit appears in gold.
Pressing this button will show potassium ions in red, zoom in on the main coordintation sites within the transmembrane segments of the alpha subunit (which now appears as light blue), and allow for easy viewing of the potassium ligands currently bound. It should be noted that the protein is in the E2 conformation.
Pressing this button will display the coordination sites which are currently bound to potassium. Site #1 residues are in green (Thr779, the main contributer with 5 oxygen atoms involved, and Ser782); residues involved in both site #1 and site #2 bonding are shown in yellow (Asn 783 and Asp 811); and water molecules involved in the binding are shown in aquamarine. The residues involved only in coordination site #2 in orange (Val 329, Ala 330, and Val 332).
Pressing this button will rotate the protein to better display the purple glycine 855 residue of the alpha subunit transmembrane helix number 7 in purple and the tyrosine 44 residue of the beta subunit (colored cyan and shown as a tube) in magenta. These two subunits interact via a hydrogren bond to cause a "kink" in the alpha membrane 7 helix which opens up the coordination sites for specific occlusion of the potassium ions in the E2 conformation.
Pressing this button will color the carboxyl terminus of the alpha subunit indianred and rotate around the molecule to get a good look at it. The carboxyl terminus uses tyrosine residues to orient the coordination sites to favor sodium instead of potassium upon reorientation to E1 (not pictured here).
Pressing this button will rotate the molecule from the coordination sites currently bound to potassium to a salt bridge between Arg 551 (blue) of the nucleotide domain located in the alpha subunit and Glu 223 (white) of the actuator domain, which is also in the alpha subunit. This salt bridge is crucial for ATP binding and manipulation of the molecule and its coordination sites. The nucleotide, actuator, and phosphorylation domains are all located on the cytoplasmic side of the molecule. Arginine has a positive charge and glutamate has a negative charge so they attracted to each other. When either amino acid is changed by DNA mutation, the pump fails to work.
© Copyright 2013 Department of Biology, Davidson College, Davidson, NC
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Send comments, questions, and suggestions to: macampbell@davidson.edu