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Identification of Asp 804 and Asp 808 as Na + and K + coordinating residues in α‐subunit of renal Na,K‐ATPase
Author(s) -
Pedersen Per Amstrup,
Rasmussen Jakob H,
Nielsen Jesper M,
Jorgensen Peter L
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(96)01381-6
Subject(s) - oligomycin , ouabain , chemistry , protein subunit , atpase , ligand (biochemistry) , crystallography , stereochemistry , biochemistry , enzyme , sodium , receptor , organic chemistry , gene
Mutations to Asp 804 and Asp 808 in the α‐subunit almost abolish Na,K‐ATPase activity, but high‐affinity binding of [ 3 H]ATP or [ 3 H]ouabain at equilibrium and E 1 –E 2 transitions are preserved. Titration of K + ‐ion displacement of [ 3 H]ATP or [ 3 H]ouabain shows that the mutations interfere with occlusion of K + in the E 2 [2K] conformation. Reduced phosphorylation levels or affinities for Na + in presence of oligomycin indicate that Asp 804 and Asp 808 also contribute to coordination of Na + in the E 1 P[3Na] form. Demonstration of alternate interactions of Na + or K + with Asp 804 and Asp 808 support the notion of cation binding in a ping‐pong sequence in catalytic models of Na,K‐pumping.