Steady-state properties of calcium binding to parvalbumins from bullfrog skeletal muscle: effects of Mg2+, pH, ionic strength, and temperature.
J Biochem
; 99(1): 73-80, 1986 Jan.
Article
em En
| MEDLINE
| ID: mdl-3485630
ABSTRACT
To improve our understanding of the physiological roles of parvalbumins, PA-1 (pI 4.78) and PA-2 (pI 4.97) parvalbumins were prepared from bullfrog skeletal muscle and their calcium binding properties were examined in a medium of constant ionic strength (I = 0.106, pH 6.80, at 20 degrees C) containing various concentrations of Mg2+ by using a metallo-indicator, tetramethylmurexide. Apparent binding constants for Ca2+ in the presence of Mg2+ changed in the manner expected if Ca2+ and Mg2+ compete for two independent homogeneous binding sites. The following values were obtained for PA-1, KCa = 1 X 10(7) M-1, KMg = 900 M-1; for PA-2, KCa = 6 X 10(6) M-1, KMg = 830 M-1 (I = 0.106, pH 6.80, at 20 degrees C). The apparent binding constants are strongly dependent on temperature at 10 degrees C for PA-1, KCa = 2 X 10(8) M-1, KMg = 10(4) M-1; for PA-2, KCa = 5 X 10(7) M-1, KMg = 5 X 10(3) M-1 (I = 0.106, pH 6.80). The dependence of the affinities for Ca2+ on ionic strength is similar to or less than that of GEDTA (EGTA). The affinities for Ca2+ and Mg2+ of parvalbumins are unchanged between pH 6.5 and 7.2.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Parvalbuminas
/
Cálcio
/
Magnésio
/
Proteínas Musculares
/
Músculos
Limite:
Animals
Idioma:
En
Revista:
J Biochem
Ano de publicação:
1986
Tipo de documento:
Article