Nakamura Shigeyoshi, Saotome Tomonori, Nakazawa Akiko, Fukuda Masao, Kuroda Yutaka, Kidokoro Shun-Ichi
Department of General Education, National Institute of Technology, Ube College , 2-14-1 Tokiwadai, Ube 755-8555, Japan.
Department of Bioengineering, Nagaoka University of Technology , 1603-1 Kamitomioka, Nagaoka 940-2188, Japan.
Biochemistry. 2017 May 9;56(18):2372-2378. doi: 10.1021/acs.biochem.6b01225. Epub 2017 May 1.
In this study, we performed differential scanning calorimetry (DSC) and pressure perturbation calorimetry (PPC) analysis of the thermal transition of cytochrome c from an acidic molten globule (MG) state with the protein concentrations of 0.5-18.2 mg/mL. DSC profiles were highly reversible and showed clear protein-concentration dependence, indicating that reversible oligomerization occurred accompanying the thermal transition from the MG state. The DSC and PPC data required at least a six-state model (MG1 ⇄ MG2 ⇄ D ⇄ / I ⇄ / I ⇄ / I) including three new oligomeric states: dimer (I), trimer (I), and tetramer (I) in addition to the three monomeric states previously characterized. Dynamic light scattering confirmed the oligomerization during the thermal transition. The partial specific volumes of these oligomeric states were found to be smaller than those of the monomeric states, MG2 and D, indicating dehydration of hydrophobic surface or hydration of released anions may occur with the reversible oligomerization.
在本研究中，我们对细胞色素c从酸性熔球态（MG）转变的热过程进行了差示扫描量热法（DSC）和压力扰动量热法（PPC）分析，蛋白质浓度范围为0.5 - 18.2 mg/mL。DSC曲线具有高度可逆性，且显示出明显的蛋白质浓度依赖性，这表明在从MG态的热转变过程中发生了可逆的寡聚化。DSC和PPC数据至少需要一个六态模型（MG1 ⇄ MG2 ⇄ D ⇄ / I ⇄ / I ⇄ / I），除了之前已表征的三个单体态外，还包括三个新的寡聚态：二聚体（I）、三聚体（I）和四聚体（I）。动态光散射证实了热转变过程中的寡聚化。发现这些寡聚态的偏比容小于单体态MG2和D的偏比容，这表明可逆寡聚化可能伴随着疏水表面的脱水或释放阴离子的水合作用。
