Nakamura K, Era S, Ozaki Y, Sogami M, Hayashi T, Murakami M
Department of Physiology, Gifu University School of Medicine, Japan.
FEBS Lett. 1997 Nov 17;417(3):375-8. doi: 10.1016/s0014-5793(97)01326-4.
Conformational changes in cystine disulfide bridges of bovine serum albumin during acid-induced isomerization (N --> F and F --> E transitions) have been studied with Raman spectroscopy. In an X-ray crystallographic study of human serum albumin, Carter and Ho reported that all disulfide bridges of the albumin molecule are in the gauche-gauche-gauche conformation [1]. On the other hand, the solution structure of bovine serum albumin examined by Raman spectroscopy differs from its crystal structure in the conformation of some of the disulfide bridges. Two Raman bands were detected at 520 and 505 cm(-1) in the disulfide stretching mode region, suggesting that the 17 disulfide bridges in the N-form of bovine serum albumin solution take both the gauche-gauche-gauche and gauche-gauche-trans conformations. The ratio of the peak intensities at 520 and 505 cm(-1) (I505/I520) is increased from 1.6 to 2.1 and from 2.1 to 6.3 on going from the N- to the F-form and from the F- to the E-form, respectively, indicating that the gauche-gauche-trans conformation of the disulfide bridges is converted to a gauche-gauche-gauche one which is the most energetically stable form during the acid-induced isomerization. However, small amounts of gauche-gauche-trans conformation still remain even in the E-form.
利用拉曼光谱研究了牛血清白蛋白在酸诱导异构化（N→F和F→E转变）过程中胱氨酸二硫键的构象变化。在一项关于人血清白蛋白的X射线晶体学研究中，卡特和何报告称白蛋白分子的所有二硫键均处于反式-反式-反式构象[1]。另一方面，通过拉曼光谱检测的牛血清白蛋白溶液结构在一些二硫键的构象上与其晶体结构不同。在二硫键伸缩模式区域，于520和505 cm⁻¹处检测到两个拉曼峰，这表明牛血清白蛋白溶液N型中的17个二硫键同时具有反式-反式-反式和顺式-反式-反式构象。从N型转变为F型以及从F型转变为E型时，520和505 cm⁻¹处峰强度的比值（I505/I520）分别从1.6增加到2.1以及从2.1增加到6.3，这表明在酸诱导异构化过程中，二硫键的顺式-反式-反式构象转变为能量上最稳定的反式-反式-反式构象。然而，即使在E型中仍保留少量的顺式-反式-反式构象。
