Brems D N, Cass R, Stellwagen E
Biochemistry. 1982 Mar 30;21(7):1488-93. doi: 10.1021/bi00536a004.
A monomeric cytochrome c containing an intramolecular disulfide bond linking residues 20 and 102 was obtained from bullfrog hearts, as previously reported by Chan et al. [Chan, S. K., Walasek, O. F., Barlow, G. H., & Margoliask, E. (1967) Fed. Proc., Fed. Am. Soc. Exp. Biol. 26, 723]. The stability of the native globular conformation of this protein is enhanced relative to that of other cytochromes c; e.g., it is stable to 0.01 N HCl in the absence of neutral salts at 25 degrees C, and its denaturation transition in guanidine at neutral pH and 25 degrees C is centered at 3.8 M. Guanidine-denatured from cytochrome c renatures in two kinetic phases whose time constants differ by about 2 orders of magnitude as observed when using other cytochromes c. However, the absolute values for the time constants of the frog protein are notably smaller. We note that the time constants for cytochromes c are inversely related to the midpoints of their guanidine transitions, suggesting that within a homologous series of proteins the more stable the conformation the faster it folds.
如Chan等人之前报道的那样[Chan, S. K., Walasek, O. F., Barlow, G. H., & Margoliask, E. (1967) Fed. Proc., Fed. Am. Soc. Exp. Biol. 26, 723]，从牛蛙心脏中获得了一种含有连接20位和102位残基的分子内二硫键的单体细胞色素c。相对于其他细胞色素c，这种蛋白质天然球状构象的稳定性有所增强；例如，在25℃无中性盐存在的情况下，它对0.01 N HCl稳定，并且在中性pH和25℃下其在胍中的变性转变中点为3.8 M。与使用其他细胞色素c时观察到的情况一样，胍变性的细胞色素c复性分为两个动力学阶段，其时间常数相差约2个数量级。然而，青蛙蛋白时间常数的绝对值明显较小。我们注意到，细胞色素c的时间常数与其胍变性转变中点呈反比关系，这表明在同源蛋白质系列中，构象越稳定，折叠速度越快。
