The Ca2+/calmodulin binding domain of the Ca2+‐ATPase linked to the Na+,K+‐ATPase alters transport stoichiometry

• Published in: FEBS letters Vol. 408; no. 3; pp. 271 - 275
• Main Authors: Zhao, Jianxing, Vasilets, Larisa A., Yoshimura, Shige H., Gu, Quanbao, Ishii, Toshiaki, Takeyasu, Kunio, Schwarz, Wolfgang
• Format: Journal Article
• Language: English
• Published: England 26-05-1997
• Subjects: Alpha-subunit; Animals; Beta-subunit; Binding Sites; Biological Transport; Calcium - metabolism; Calcium-Transporting ATPases - biosynthesis; Calcium-Transporting ATPases - chemistry; Calcium-Transporting ATPases - metabolism; Calmodulin; Calmodulin - metabolism; Cell Membrane - physiology; Chickens; Electrogenicity; Female; Ion (Na+) transport; Kinetics; Membrane Potentials; Oocytes - physiology; Ouabain - pharmacology; Patch-Clamp Techniques; Rats; Recombinant Fusion Proteins - biosynthesis; Recombinant Fusion Proteins - metabolism; Rubidium - metabolism; Sodium - metabolism; Sodium pump; Sodium-Potassium-Exchanging ATPase - biosynthesis; Sodium-Potassium-Exchanging ATPase - chemistry; Sodium-Potassium-Exchanging ATPase - metabolism; Xenopus laevis
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(97)00435-3

Using Xenopus oocytes as an expression system, we have investigated ion‐transport and ouabain‐binding properties of a chimeric ATPase (α1‐CBD; Ishii and Takeyasu (1995) EMBO J. 14, 58–67) formed by the α1‐subunit of chicken Na+,K+‐ATPase (α1) and the calmodulin binding domain (CBD) of the rat plasma membrane Ca2+‐ATPase. α1‐CBD can be expressed and transported to the oocyte plasma membrane without the β‐subunit, and shows ouabain binding. In contrast to ouabain binding, this chimera requires the β‐subunit for its cation (Na+ and K+) transport activity. α1‐CBD exhibits an altered stoichiometry of Na+‐K+ exchange. A detailed analysis of 22Na+ efflux, 86Rb+ uptake, pump current and ouabain binding suggests that the chimeric molecule can operate in an electrically silent 2Na+–2K+ exchange mode and, with much lower probability, in its normal 3Na+–2K+ exchange mode.