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The Na + ,K + ‐ATPase carrying the carboxy‐terminal Ca 2+ /calmodulin binding domain of the Ca 2+ pump has 2Na + ,2K + stoichiometry and lost charge movement in Na + /Na + exchange
Author(s) -
Yoshimura Shige H,
Vasilets Larisa A,
Ishii Toshiaki,
Takeyasu Kunio,
Schwarz Wolfgang
Publication year - 1998
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(98)00202-6
Subject(s) - physics , calmodulin , crystallography , chemistry , enzyme , nuclear magnetic resonance
An altered ion‐transport stoichiometry from 3Na + ,2K + to 2Na + ,2K + is observed in a chimeric Na + ,K + ‐ATPase, which carries the Ca 2+ /calmodulin binding domain (CBD) of the plasma membrane Ca 2+ ‐ATPase at its carboxy‐terminus [Zhao et al., FEBS Lett. 408 (1997) 271–275]. The ouabain‐resistant mutant of this chimera (ORα1‐CBD) was constructed to further investigate the effect of the CBD on ion‐transport properties. The ORα1‐CBD still shows the 2Na + ,2K + stoichiometry. The loss of electrogenicity is accompanied by the disappearance of transient charge movements in the Na + /Na + exchange mode. We conclude that the binding of the third Na + ion, but not of the two others, in 3Na + ,2K + transport mode apparently senses the electric field, and that the voltage‐dependent Na + binding is likely to be lost in the chimera with CBD.