The C-terminal 165 amino acids of the plasma membrane Ca(2+)-ATPase confer Ca2+/calmodulin sensitivity on the Na+,K(+)-ATPase alpha-subunit.
The C-terminal 165 amino acids of the rat brain plasma membrane (PM) Ca(2+)-ATPase II containing the calmodulin binding auto-inhibitory domain was connected to the C-terminus of the ouabain sensitive chicken Na+,K(+)-ATPase alpha 1 subunit. Expression of this chimeric molecule in ouabain resistant mouse L cells was assured by the high-affinity binding of [3H]ouabain. In the presence of Ca2+/calmodulin, this chimeric molecule exhibited ouabain inhibitable Na+,K(+)-ATPase activity; the putative chimeric ATPase activity was absent in the absence of Ca2+/calmodulin and activated by Ca2+/calmodulin in a dose-dependent manner. Furthermore, this chimeric molecule could bind monoclonal IgG 5 specific to the chicken Na+,K(+)-ATPase alpha 1 subunit only in the presence of Ca2+/calmodulin, suggesting that the epitope for IgG 5 in this chimera is masked in the absence of Ca2+/calmodulin and uncovered in their presence. These results propose a direct interaction between the calmodulin binding auto-inhibitory domain of the PM Ca(2+)-ATPase and the specific regions of the Na+,K(+)-ATPase alpha 1 subunit that are structurally homologous to the PM Ca(2+)-ATPase. A comparison of the deduced amino acid sequences revealed several possible regions within the Na+,K(+)-ATPase that might interact with the auto-inhibitory domain of the PM Ca(2+)-ATPase.
Ishii
T
T
Department of Medical Biochemistry, Ohio State University, Columbus 43210.
Takeyasu
K
K
D000251:Adenosine Triphosphatases / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism* / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D007739:L Cells; D051379:Mice; D008969:Molecular Sequence Data; D010042:Ouabain / Q000378:metabolism / Q000494:pharmacology; D011233:Precipitin Tests; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000276:immunology / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D013329:Structure-Activity Relationship
D002147:Calmodulin; D011993:Recombinant Fusion Proteins; D010042:Ouabain; D000251:Adenosine Triphosphatases; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium