细胞色素C与细胞色素氧化酶之间相互作用的共振RAMAN光谱研究

STUDY ON THE INTERACTION BETWEEN CYTOCHROME C AND CYTOCHROME OXIDASE WITH RESONANCE SPECTROSCORY

分别于５１４．５ｎｍ及６０４ｕｍ波长激发下，对游离的细胞色素Ｃ，细胞色素氧化酶以及细胞色素Ｃ和细胞色素氧化酶的复合体的共振拉曼光谱进行了分析比较，在形成复合体时，双方蛋白的共振拉曼谱均有所变化，一个共同的特征性变化是Ａ２ｇｖ２２１１３０ｃｍ－１，ｖ２１１３１２ｃｍ－１，ｖ２０１４００ｃｍ－２，和ｖ１９１５８４ｃｍ－１强度都有增强，其中变化最明显的是Ａ２ｇｖ１９１５８４ｃｍ－１峰，在游离态中，Ｉ１５４０／ｉ１５８２＞１，在结合态中Ｉ１５５０／Ｉ１５８２＜１。

Cytochrome c oxidase is the terminal electron tiansfer enzyme of mitochondrial respiratory chain. It accepts electron from reduced cytochrome c and transfers them to oxygen. The frist event happened in the eleetron tiansferring from cytochrome c to cytochrome oxidase is to form a transient complex of them.The surface positive-charge localization on the cytochrome molecule serves to orient the molecule such that its heme prothetic group makes direct and alternate interaction with the prosthetic groups of cytochrome oxidase. This binding is important for both sides of heme prosthetic groups to lower the barrier of electron transferring be tween them. To study the physical properties of this hansfer complex, especially the changes of heme groups upon the intetaction of the two proteins is helpful to understand the mechanisims of electron tiansferring beween cytochromes. In the present work we take the advantage of excitation at 514.5nm and 604um where Raman bands of heme c and heme a groups are separately and selectively enhanced.The resonance Raman spectra of the free states of cytochrome c, cytochrome oxidase and the complex of them were studied. We found that some A2g vibrational modes of v22 1130, v211312, v201399, and v19 1584cm-1, were increased on both sides of heme c and heme a when the enzymes changed from free state to bound sae. A remarkable change was seen in the ratio of I1584/I1545 which is less than 1 in the free state and larger than 1 in the bound state.The changes of asonace Raman spectra reflect the environmetal changes of groups caused by the inthection of proteins as they combined with each other. The signal we obtained in the resonsance Raman spectra excised at 604nm are mianly that of heme a. As such, the binding of proteins made the hare prosthetic groups orient mutually and ease the electron thensferring.