非双层脂对辅酶Q-细胞色素c还原酶呼吸控制率的影响

THE EFFECT OF NONBILAYER PHOSPHOLIPIDS ON THE RESPIRATORY CONTROL RATIO OF UBIQUENOL-CYTOCHROME C REDUCTAS

分离提纯的辅酶Q细胞色素c还原酶经胆酸盐透析法重组于各种脂质体上,发现脂质体中PE含量的升高可显著提高辅酶Q-细胞色素c还原酶的呼吸控制率.在PE含量为60%-80%时达到最高值,DOPE的L_x—H_Ⅱ的相变温度显著低于DEPE,脂酶体中DOPE含量的提高,可显著提高酶的呼吸控制率,而DEPE的影响很小,改变脂酶体中心磷脂的含量对呼吸控制率的影响较小.含有PE脂酶体中酶的CD谱419nm处的正峰,随PE含量的增大而增强,表明酶蛋白中血红素辅基的微环境有所改变.NBD-DOPE标记脂酶体研究了不同脂酶体的 L_x-H_Ⅱ的相变性质,表明PE含量的降低脂质体的相变温度上升甚至消失.

Mitochondrial inner membrane are rich in nonbilayer phospholipids (PE and cardiolipin) whose function remains elusive, Ubiquinol - cytochrome c reductase (complex Ⅲ ) was purified from bovine heart mitochondria and reconstituted complex Ⅲ containing liposomes with higher respiratory control ratio was prepared. The respiratory control ratio of the reconstituted enzyme complex into PC + PE liposomes becomes higher (from 2.5 to 10.0) as the PE content increases (from 0- 100%). The hishest respiratory control ratio was obtained with 80% PE containing proteoliposomes. The Lα -H Ⅱ phase transition temperature of DOPE (13℃) proteoliposomes. If the complex Ⅲ was reconstituted with PC + DOPE, the respiratory control ratio enhanced from 2.5 to 14.0 as the DOPE content increases from 0 to 45%, but no obvious change could be observed if the DOPE was replaosd by DEPE. Cardiolipin has a little effect on the respiratory control ratio of the reconsituted proteoliposomes. The Lα-H Ⅱ transition temperature of PE containing proteoliposomes determined by NBD -DOPE increases as PE content decreases. The peak height at 419nm of CD spectra of the complex Ⅲ containing proteoliposome increases with increasing PE content.From the above result, it is tentatively suggested that the increase of the nonbilayer lipid structure formation tendency could lead to a nonstable and more flexible membrane structure, which may be important for the appearance of a suitable conformation of complex Ⅲ with higher enzymatic activity.