Identification of calmodulin-sensitive Ca(2+)-transporting ATPase in the plasma membrane of bovine corneal epithelial cell.
Biochim Biophys Acta
; 1068(1): 1-8, 1991 Sep 10.
Article
em En
| MEDLINE
| ID: mdl-1832560
ATP-dependent Ca2+ uptake was characterized in a plasma membrane enriched fraction obtained from the bovine corneal epithelium. This uptake essentially represented intravesicular accumulation because 72% of the Ca2+ content was releasable following exposure to 10(-6) M A23187. The substrate and Ca2+ requirements for maximal transport activity were similar to those described in the red blood cell because: (1) exogenous calmodulin (3 microM) significantly decreased the apparent Km for Ca2+ to 0.31 microM and increased the rate of Ca2+ uptake; (2) a hydroxylamine labile Ca(2+)-dependent phosphoenzyme intermediate was identified with an apparent molecular size of 140 kDa; (3) Ca(2+)-dependent binding of 125I-labelled calmodulin to this protein was demonstrated which could be antagonized with a calmodulin antagonist, trifluoperazine. These results show that the plasma membrane contains an ATP-dependent Ca2+ transporter. However, its relationship to a previously described high affinity form of Ca(2+)-stimulated Mg(2+)-dependent ATPase is not apparent because their [Mg2+] requirements to elicit maximal activity differed by two orders of magnitude.
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Base de dados:
MEDLINE
Assunto principal:
Calmodulina
/
Proteínas de Transporte
/
Membrana Celular
/
ATPases Transportadoras de Cálcio
/
Córnea
Tipo de estudo:
Diagnostic_studies
/
Prognostic_studies
Limite:
Animals
Idioma:
En
Ano de publicação:
1991
Tipo de documento:
Article