Dual activity of the H1-H2 domain of the (Na(+)+K+)-ATPase.
Biochem Biophys Res Commun
; 377(2): 469-473, 2008 Dec 12.
Article
em En
| MEDLINE
| ID: mdl-18848919
ABSTRACT
(Na(+)+K(+))-ATPase is a target receptor of digitalis (cardiac glycoside) drugs. It has been demonstrated that the H1-H2 domain of the alpha-subunit of the (Na(+)+K(+))-ATPase is one of the digitalis drug interaction sites of the enzyme. Despite the extensive studies of the inhibitory effect of digitalis on the (Na(+)+K(+))-ATPase, the functional property of the H1-H2 domain of the enzyme and its role in regulating enzyme activity is not completely understood. Here we report a surprise finding:
instead of inhibiting the enzyme, binding of a specific monoclonal antibody SSA78 to the H1-H2 domain of the (Na(+)+K(+))-ATPase elevates the catalytic activity of the enzyme. In the presence of low concentration of ouabain, monoclonal antibody SSA78 significantly protects enzyme function against ouabain-induced inhibition. However, higher concentration of ouabain completely inactivates the (Na(+)+K(+))-ATPase even in the presence of SSA78. These results suggest that the H1-H2 domain of the (Na(+)+K(+))-ATPase is capable of regulating enzyme function in two distinct ways for both ouabain-sensitive and -resistant forms of the enzyme it increases the activity of the (Na(+)+K(+))-ATPase during its interaction with an activator; it also participates in the mechanism of digitalis or ouabain-induced inhibition of the enzyme. Understanding the dual activity of the H1-H2 domain will help better understand the structure-function relationships of the (Na(+)+K(+))-ATPase and the biological processes mediated by the enzyme.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
ATPase Trocadora de Sódio-Potássio
Limite:
Animals
Idioma:
En
Revista:
Biochem Biophys Res Commun
Ano de publicação:
2008
Tipo de documento:
Article