Moosavi-Movahedi A A, Chamani J, Ghourchian H, Shafiey H, Sorenson C M, Sheibani N
Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
J Protein Chem. 2003 Jan;22(1):23-30. doi: 10.1023/a:1023011609931.
The molten globule state (MG) of cytochrome c is the major intermediate of protein folding. The formation of MG state of cytochrome c is induced by n-alkyl sulfates such as sodium octyl sulfate (SOS), sodium dodecyl sulfate (SDS), and sodium tetradecyl sulfate (STS). The folding state of cytochrome c was monitored using circular dichroism (CD), isothermal titration calorimetry (ITC) and partial specific volumes. To explore a new approach for characterizing the MG conformation, cyclic voltametric studies of n-alkyl sulfates induced transition at acidic pH of cytochrome c (unfolded state, U) was carried out. Here, we have used a cystein-modified gold electrode, which is effective for direct rapid electron transfer to cytochrome c even in acid solutions, to directly observe electrochemistry in native (N) cytochrome c. Our results show that the extent of electron transfer is increased for U --> MG, and also the easiness of electron transferring occurred from MG --> N transition. Thus we demonstrate that the MG state of cytochrome c, induced by n-alkyl sulfates as salts with hydrophobic chains (hydrophobic salts), with different compactness reaches to near identical amount of electron transferring as N state.
细胞色素c的熔球态（MG）是蛋白质折叠的主要中间体。细胞色素c的MG态形成是由正烷基硫酸盐诱导的，如辛基硫酸钠（SOS）、十二烷基硫酸钠（SDS）和十四烷基硫酸钠（STS）。利用圆二色性（CD）、等温滴定量热法（ITC）和比容监测细胞色素c的折叠状态。为了探索一种表征MG构象的新方法，我们进行了正烷基硫酸盐诱导细胞色素c在酸性pH下（未折叠态，U）转变的循环伏安研究。在这里，我们使用了一种半胱氨酸修饰的金电极，即使在酸性溶液中它也能有效地将电子直接快速转移到细胞色素c上，从而直接观察天然态（N）细胞色素c的电化学过程。我们的结果表明，从U态到MG态电子转移程度增加，并且从MG态到N态转变时电子转移更容易发生。因此我们证明，由带有疏水链的盐（疏水性盐）正烷基硫酸盐诱导的细胞色素c的MG态，尽管具有不同的紧密程度，但达到了与N态几乎相同的电子转移量。
