Steady-state properties of calcium binding to parvalbumins from bullfrog skeletal muscle: effects of Mg2+, pH, ionic strength, and temperature.
Steady-state properties of calcium binding to parvalbumins from bullfrog skeletal muscle: effects of Mg2+, pH, ionic strength, and temperature.
复制标题
钙与牛蛙骨骼肌小白蛋白结合的稳态特性：Mg2、pH、离子强度和温度的影响。
DOI：
10.1093/oxfordjournals.jbchem.a135481
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发表时间：
1986
影响因子：
2.7
通讯作者：
Masaru Tanokura
中科院分区：
文献类型：
--
作者：
Y. Ogawa;Masaru Tanokura
为了提高我们对小清蛋白生理作用的理解，PA-1（pI 4.78）和PA-2从牛蛙骨骼肌中制备了pI为4.97的小清蛋白，并在恒定离子强度的介质中研究了它们的钙结合特性（I = 0.106，pH 6.80，在20 ℃下）含有不同浓度的Mg 2+。在Mg 2+存在下，Ca 2+的表观结合常数以预期的方式变化，如果Ca 2+和Mg 2+竞争两个独立的均质结合位点。获得以下值：对于PA-1，KCa = 1 × 10（7）M-1，KMg = 900 M-1;对于PA-2，KCa = 6 × 10（6）M-1，KMg = 830 M-1（I = 0.106，pH 6.80，20 ℃）。表观结合常数强烈依赖于温度：在10 ℃时，PA-1的KCa = 2 × 10（8）M-1，KMg = 10（4）M-1; PA-2的KCa = 5 × 10（7）M-1，KMg = 5 × 10（3）M-1（I = 0.106，pH 6.80）。对Ca ~（2+）的亲和力对离子强度的依赖性类似于或小于GEDTA（EGTA）。小清蛋白对Ca ~（2+）和Mg ~（2+）的亲和力在pH 6.5和7.2之间不变。
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.