Kawamura-Konishi Y, Suzuki H
J Biochem. 1985 Nov;98(5):1181-90. doi: 10.1093/oxfordjournals.jbchem.a135384.
Binding of hemin to globin was studied in the presence of 25 mM caffeine by measuring CD and optical absorption changes in the Soret region. CD and optical absorption spectra after mixing equimolar amounts of hemin and globin were the same as those of ferric hemoglobin. In contrast, addition of excess globin to hemin formed a complex that was distinguishable from ferric hemoglobin in terms of the CD and optical absorption spectra. By comparing the spectra of the complex with those of various hemoglobin derivatives, it was concluded that the complex was globin which carried a hemin exclusively on the alpha chain. This means that the alpha chain of the globin molecule has a greater affinity for hemin than the beta chain, as observed by other investigators using hemin-cyanide. The rate of binding of hemin to globin was estimated by the use of CD and optical absorption stopped-flow apparatus. The rate of hemin binding to the alpha chain of globin was obtained by mixing hemin and excess globin, and that to the beta chain was obtained by mixing equimolar concentrations of hemin and globin. The results showed that hemin was bound to the alpha chain in the globin molecule to form a transient intermediate, followed by its transformation into another intermediate, the transformation was the rate-limiting step, and the beta chain in the globin molecule had a greater affinity for hemin after hemin binding to the alpha chain than before.
在25 mM咖啡因存在的情况下，通过测量索雷特区域的圆二色性（CD）和光吸收变化，研究了血红素与珠蛋白的结合。将等摩尔量的血红素和珠蛋白混合后的CD和光吸收光谱与高铁血红蛋白的光谱相同。相比之下，向血红素中加入过量的珠蛋白形成了一种复合物，该复合物在CD和光吸收光谱方面与高铁血红蛋白不同。通过将该复合物的光谱与各种血红蛋白衍生物的光谱进行比较，得出该复合物是仅在α链上携带一个血红素的珠蛋白。这意味着珠蛋白分子的α链对血红素的亲和力大于β链，这与其他研究人员使用血红素 - 氰化物观察到的结果一致。通过使用CD和光吸收停流装置估计血红素与珠蛋白的结合速率。血红素与珠蛋白α链的结合速率是通过将血红素和过量的珠蛋白混合得到的，而与β链的结合速率是通过将等摩尔浓度的血红素和珠蛋白混合得到的。结果表明，血红素与珠蛋白分子中的α链结合形成一个瞬时中间体，随后转化为另一个中间体，该转化是限速步骤，并且在血红素与α链结合后，珠蛋白分子中的β链对血红素的亲和力比之前更大。
