The active species of plasma membrane Ca2+-ATPase are a dimer and a monomer-calmodulin complex.
J Biol Chem
; 271(17): 9987-91, 1996 Apr 26.
Article
en En
| MEDLINE
| ID: mdl-8626638
ABSTRACT
The purified plasma membrane Ca2+-ATPase is fully activated through the enzyme concentration-dependent self-association at physiologically relevant Ca2+ concentrations (Kosk-Kosicka, D., and Bzdega, T. (1988) J. Biol. Chem. 263, 18184-18189; Kosk-Kosicka, D., Bzdega, T., and Wawrzynow, A. (1989) J. Biol. Chem. 264, 19495-19499). We have previously shown that the Ca2+-ATPase activity of the oligomeric enzyme is independent of calmodulin, in contrast to another active enzyme species, a presumable monomer, that is activated by calmodulin binding. Presently, we have succeeded in determining the molecular mass of the two active enzyme species by equilibrium ultracentrifugation. For the calmodulin-dependent species, the molecular mass is 170 +/- 30 kDa, which is consistent with predominantly monomeric Ca2+-ATPase with bound calmodulin. The molecular mass of calmodulin-independent oligomers is 260 +/- 34 kDa, indicating that they are dimers. Results of experiments performed under different calcium and potassium concentrations and in the presence of dextran that causes molecular crowding verify a strict Ca2+ requirement of the dimerization process. We conclude that the active species of the Ca2+-ATPase are a monomer-calmodulin complex and a dimer.
Buscar en Google
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Proteínas de Unión a Calmodulina
/
Calmodulina
/
ATPasas Transportadoras de Calcio
/
Membrana Eritrocítica
Límite:
Humans
Idioma:
En
Revista:
J Biol Chem
Año:
1996
Tipo del documento:
Article
País de afiliación:
Estados Unidos