CONFORMATION, CO-OPERATIVITY AND LIGAND-BINDING IN HUMAN HEMOGLOBIN
CONFORMATION, CO-OPERATIVITY AND LIGAND-BINDING IN HUMAN HEMOGLOBIN
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DOI：
10.1016/0022-2836(75)90382-4
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发表时间：
1975-01-01
影响因子：
5.6
通讯作者：
GIBSON, QH
中科院分区：
文献类型：
--
作者：
CASSOLY, R;GIBSON, QH
似乎没有任何协同性表现在四个组合速率常数的结合一氧化氮脱氧血红蛋白。所观察到的反应的时间过程最好由统计相关速率拟合，并且可以独立获得的第四个一氧化碳分子和第四个一氧化氮分子的结合速率常数之间的数值关系也证明了一氧化氮结合速率常数之间的统计关系。正常的T → R转换发生在一氧化氮结合上，如8-羟基-1，3，6-芘三磺酸盐的释放所证明的，R-状态显示出与T-状态相比对一氧化碳的反应性的正常增强（30倍）一氧化碳和一氧化氮同时与脱氧血红蛋白反应的竞争实验表明，转换点（T → R）平均在2.7个一氧化氮分子被结合后（在0.05m-2，2-双（羟甲基）-2，2 Mobi，2 ″-次氮基三乙醇中，pH 7）和3个一氧化碳分子被结合后（在0.05m-磷酸盐中，pH 7）发生。
There does not appear to be any co-operativity manifest in the four combination rate constants for the binding of nitric oxide to deoxyhemoglobin. The time-course of the observed reaction is best fitted by statistically related rates, and the numerical relation between the rate constants for the binding of the fourth molecule of carbon monoxide and the fourth molecule of nitric oxide, which can be obtained independently, also argues for a statistical relation between the nitric oxide binding rate constants.In spite of the absence of co-operativity, the normal T → R transition occurs on nitric oxide binding, as demonstrated by the release of 8-hydroxy-1,3,6-pyrene trisulfonate, and the R-state shows the normal enhancement of reactivity towards carbon monoxide as compared with the T-state (30-fold).Competition experiments between carbon monoxide and nitric oxide in which the two ligands react simultaneously with deoxyhemoglobin suggest that the switching point (T → R) occurs on the average after 2.7 molecules of nitric oxide have been bound (in 0.05m-2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol, pH 7) and after 3 molecules of carbon monoxide (in 0.05m-phosphate, PH 7).