Yang F Y, Wang X S, Tong J C, Han X H
National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Beijing, People's Republic of China.
Biochem Mol Biol Int. 1993 Aug;30(5):867-76.
Chemically-prepared chicken heart apocytochrome c with different unfolded states could be obtained during the renaturation process. They exhibited distinct circular dichroism patterns designated as Apo C1 (random coiled), Apo C2 (less ordered) and Apo C3 (more ordered). This characteristic is unique to chicken heart apocytochrome c while compared with its counterparts from Candida krusei, tuna heart or horse heart and promises the emergence of much more detail of correlation of translocation with unfolded states of apocytochrome c. When chicken heart apocytochrome c was subjected to a translocation assay in vitro using trypsin-enclosed large unilamellar vesicles from soybean phospholipids, the ability of the protein to penetrate into the liposomes was found to follow the order of Apo C1 > Apo C2 > Apo C3. Conformational alterations of Apo C1, Apo C2 and Apo C3 in association with soybean phospholipid vesicles shown by circular dichroism measurement demonstrated that Apo C1 bound to phospholipids existed in a more loosely folded conformation than Apo C2 and Apo C3. We propose that a more flexible structure of apocytochrome c following the interaction with phospholipids is required for its efficient translocation across the bilayer.
在复性过程中可获得具有不同未折叠状态的化学合成鸡心脱辅基细胞色素c。它们呈现出不同的圆二色性图谱，分别命名为Apo C1（无规卷曲）、Apo C2（有序程度较低）和Apo C3（有序程度较高）。与克鲁斯假丝酵母、金枪鱼心脏或马心脏来源的对应物相比，这一特性是鸡心脱辅基细胞色素c所特有的，并且有望揭示脱辅基细胞色素c的转运与未折叠状态之间更多详细的相关性。当使用来自大豆磷脂的包封胰蛋白酶的大单层囊泡对鸡心脱辅基细胞色素c进行体外转运测定时，发现该蛋白质穿透脂质体的能力遵循Apo C1 > Apo C2 > Apo C3的顺序。通过圆二色性测量显示的Apo C1、Apo C2和Apo C3与大豆磷脂囊泡相关的构象变化表明，与磷脂结合的Apo C1以比Apo C2和Apo C3更松散折叠的构象存在。我们提出，脱辅基细胞色素c与磷脂相互作用后需要更灵活的结构才能有效地跨双层转运。
